diff --git a/components/script/build.rs b/components/script/build.rs
index bf496fb48f3..1e98ab5382c 100644
--- a/components/script/build.rs
+++ b/components/script/build.rs
@@ -50,7 +50,7 @@ fn main() {
     let mut phf = File::create(&phf).unwrap();
     write!(
         &mut phf,
-        "pub static MAP: phf::Map<&'static [u8], unsafe fn(JSContext, HandleObject)> = "
+        "pub static MAP: phf::Map<&'static [u8], fn(JSContext, HandleObject)> = "
     )
     .unwrap();
     map.build(&mut phf).unwrap();
diff --git a/components/script/compartments.rs b/components/script/compartments.rs
index c26e72ccd1a..7b45f38c56a 100644
--- a/components/script/compartments.rs
+++ b/components/script/compartments.rs
@@ -4,7 +4,8 @@
 
 use crate::dom::bindings::reflector::DomObject;
 use crate::dom::globalscope::GlobalScope;
-use js::jsapi::{GetCurrentRealmOrNull, JSAutoRealm, JSContext};
+use crate::script_runtime::JSContext;
+use js::jsapi::{GetCurrentRealmOrNull, JSAutoRealm};
 
 pub struct AlreadyInCompartment(());
 
@@ -17,9 +18,9 @@ impl AlreadyInCompartment {
         AlreadyInCompartment(())
     }
 
-    pub fn assert_for_cx(cx: *mut JSContext) -> AlreadyInCompartment {
+    pub fn assert_for_cx(cx: JSContext) -> AlreadyInCompartment {
         unsafe {
-            assert!(!GetCurrentRealmOrNull(cx).is_null());
+            assert!(!GetCurrentRealmOrNull(*cx).is_null());
         }
         AlreadyInCompartment(())
     }
diff --git a/components/script/dom/audiobuffer.rs b/components/script/dom/audiobuffer.rs
index 4b113a200fe..b0772d8b2af 100644
--- a/components/script/dom/audiobuffer.rs
+++ b/components/script/dom/audiobuffer.rs
@@ -13,10 +13,10 @@ use crate::dom::bindings::num::Finite;
 use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
 use crate::dom::bindings::root::DomRoot;
 use crate::dom::window::Window;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use dom_struct::dom_struct;
 use js::jsapi::JS_GetArrayBufferViewBuffer;
-use js::jsapi::{Heap, JSContext, JSObject};
+use js::jsapi::{Heap, JSObject};
 use js::rust::wrappers::DetachArrayBuffer;
 use js::rust::CustomAutoRooterGuard;
 use js::typedarray::{CreateWith, Float32Array};
@@ -127,7 +127,7 @@ impl AudioBuffer {
     }
 
     #[allow(unsafe_code)]
-    unsafe fn restore_js_channel_data(&self, cx: *mut JSContext) -> bool {
+    fn restore_js_channel_data(&self, cx: JSContext) -> bool {
         let _ac = enter_realm(&*self);
         for (i, channel) in self.js_channels.borrow_mut().iter().enumerate() {
             if !channel.get().is_null() {
@@ -135,20 +135,22 @@ impl AudioBuffer {
                 continue;
             }
 
-            rooted!(in (cx) let mut array = ptr::null_mut::<JSObject>());
+            rooted!(in (*cx) let mut array = ptr::null_mut::<JSObject>());
             if let Some(ref shared_channels) = *self.shared_channels.borrow() {
                 // Step 4. of
                 // https://webaudio.github.io/web-audio-api/#acquire-the-content
                 // "Attach ArrayBuffers containing copies of the data to the AudioBuffer,
                 // to be returned by the next call to getChannelData()".
-                if Float32Array::create(
-                    cx,
-                    CreateWith::Slice(&shared_channels.buffers[i]),
-                    array.handle_mut(),
-                )
-                .is_err()
-                {
-                    return false;
+                unsafe {
+                    if Float32Array::create(
+                        *cx,
+                        CreateWith::Slice(&shared_channels.buffers[i]),
+                        array.handle_mut(),
+                    )
+                    .is_err()
+                    {
+                        return false;
+                    }
                 }
             }
             channel.set(array.get());
@@ -231,16 +233,15 @@ impl AudioBufferMethods for AudioBuffer {
 
     // https://webaudio.github.io/web-audio-api/#dom-audiobuffer-getchanneldata
     #[allow(unsafe_code)]
-    fn GetChannelData(&self, cx: SafeJSContext, channel: u32) -> Fallible<NonNull<JSObject>> {
+    fn GetChannelData(&self, cx: JSContext, channel: u32) -> Fallible<NonNull<JSObject>> {
         if channel >= self.number_of_channels {
             return Err(Error::IndexSize);
         }
 
+        if !self.restore_js_channel_data(cx) {
+            return Err(Error::JSFailed);
+        }
         unsafe {
-            if !self.restore_js_channel_data(*cx) {
-                return Err(Error::JSFailed);
-            }
-
             Ok(NonNull::new_unchecked(
                 self.js_channels.borrow()[channel as usize].get(),
             ))
@@ -307,7 +308,7 @@ impl AudioBufferMethods for AudioBuffer {
         }
 
         let cx = self.global().get_cx();
-        if unsafe { !self.restore_js_channel_data(*cx) } {
+        if !self.restore_js_channel_data(cx) {
             return Err(Error::JSFailed);
         }
 
diff --git a/components/script/dom/bindings/callback.rs b/components/script/dom/bindings/callback.rs
index 03b8f326f55..6059d75605a 100644
--- a/components/script/dom/bindings/callback.rs
+++ b/components/script/dom/bindings/callback.rs
@@ -13,10 +13,10 @@ use crate::dom::bindings::settings_stack::{AutoEntryScript, AutoIncumbentScript}
 use crate::dom::bindings::utils::AsCCharPtrPtr;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::window::Window;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use js::jsapi::Heap;
 use js::jsapi::JSAutoRealm;
-use js::jsapi::{AddRawValueRoot, IsCallable, JSContext, JSObject};
+use js::jsapi::{AddRawValueRoot, IsCallable, JSObject};
 use js::jsapi::{EnterRealm, LeaveRealm, Realm, RemoveRawValueRoot};
 use js::jsval::{JSVal, ObjectValue, UndefinedValue};
 use js::rust::wrappers::{JS_GetProperty, JS_WrapObject};
@@ -82,11 +82,11 @@ impl CallbackObject {
     }
 
     #[allow(unsafe_code)]
-    unsafe fn init(&mut self, cx: *mut JSContext, callback: *mut JSObject) {
+    unsafe fn init(&mut self, cx: JSContext, callback: *mut JSObject) {
         self.callback.set(callback);
         self.permanent_js_root.set(ObjectValue(callback));
         assert!(AddRawValueRoot(
-            cx,
+            *cx,
             self.permanent_js_root.get_unsafe(),
             b"CallbackObject::root\n".as_c_char_ptr()
         ));
@@ -113,7 +113,7 @@ impl PartialEq for CallbackObject {
 /// callback interface types.
 pub trait CallbackContainer {
     /// Create a new CallbackContainer object for the given `JSObject`.
-    unsafe fn new(cx: SafeJSContext, callback: *mut JSObject) -> Rc<Self>;
+    unsafe fn new(cx: JSContext, callback: *mut JSObject) -> Rc<Self>;
     /// Returns the underlying `CallbackObject`.
     fn callback_holder(&self) -> &CallbackObject;
     /// Returns the underlying `JSObject`.
@@ -152,8 +152,8 @@ impl CallbackFunction {
 
     /// Initialize the callback function with a value.
     /// Should be called once this object is done moving.
-    pub unsafe fn init(&mut self, cx: SafeJSContext, callback: *mut JSObject) {
-        self.object.init(*cx, callback);
+    pub unsafe fn init(&mut self, cx: JSContext, callback: *mut JSObject) {
+        self.object.init(cx, callback);
     }
 }
 
@@ -179,18 +179,18 @@ impl CallbackInterface {
 
     /// Initialize the callback function with a value.
     /// Should be called once this object is done moving.
-    pub unsafe fn init(&mut self, cx: SafeJSContext, callback: *mut JSObject) {
-        self.object.init(*cx, callback);
+    pub unsafe fn init(&mut self, cx: JSContext, callback: *mut JSObject) {
+        self.object.init(cx, callback);
     }
 
     /// Returns the property with the given `name`, if it is a callable object,
     /// or an error otherwise.
-    pub fn get_callable_property(&self, cx: *mut JSContext, name: &str) -> Fallible<JSVal> {
-        rooted!(in(cx) let mut callable = UndefinedValue());
-        rooted!(in(cx) let obj = self.callback_holder().get());
+    pub fn get_callable_property(&self, cx: JSContext, name: &str) -> Fallible<JSVal> {
+        rooted!(in(*cx) let mut callable = UndefinedValue());
+        rooted!(in(*cx) let obj = self.callback_holder().get());
         unsafe {
             let c_name = CString::new(name).unwrap();
-            if !JS_GetProperty(cx, obj.handle(), c_name.as_ptr(), callable.handle_mut()) {
+            if !JS_GetProperty(*cx, obj.handle(), c_name.as_ptr(), callable.handle_mut()) {
                 return Err(Error::JSFailed);
             }
 
@@ -206,16 +206,12 @@ impl CallbackInterface {
 }
 
 /// Wraps the reflector for `p` into the compartment of `cx`.
-pub fn wrap_call_this_object<T: DomObject>(
-    cx: *mut JSContext,
-    p: &T,
-    mut rval: MutableHandleObject,
-) {
+pub fn wrap_call_this_object<T: DomObject>(cx: JSContext, p: &T, mut rval: MutableHandleObject) {
     rval.set(p.reflector().get_jsobject().get());
     assert!(!rval.get().is_null());
 
     unsafe {
-        if !JS_WrapObject(cx, rval) {
+        if !JS_WrapObject(*cx, rval) {
             rval.set(ptr::null_mut());
         }
     }
@@ -228,7 +224,7 @@ pub struct CallSetup {
     /// (possibly wrapped) callback object.
     exception_global: DomRoot<GlobalScope>,
     /// The `JSContext` used for the call.
-    cx: *mut JSContext,
+    cx: JSContext,
     /// The compartment we were in before the call.
     old_realm: *mut Realm,
     /// The exception handling used for the call.
@@ -255,7 +251,7 @@ impl CallSetup {
         let ais = callback.incumbent().map(AutoIncumbentScript::new);
         CallSetup {
             exception_global: global,
-            cx: *cx,
+            cx: cx,
             old_realm: unsafe { EnterRealm(*cx, callback.callback()) },
             handling: handling,
             entry_script: Some(aes),
@@ -264,7 +260,7 @@ impl CallSetup {
     }
 
     /// Returns the `JSContext` used for the call.
-    pub fn get_context(&self) -> *mut JSContext {
+    pub fn get_context(&self) -> JSContext {
         self.cx
     }
 }
@@ -272,13 +268,13 @@ impl CallSetup {
 impl Drop for CallSetup {
     fn drop(&mut self) {
         unsafe {
-            LeaveRealm(self.cx, self.old_realm);
+            LeaveRealm(*self.cx, self.old_realm);
             if self.handling == ExceptionHandling::Report {
                 let _ac = JSAutoRealm::new(
-                    self.cx,
+                    *self.cx,
                     self.exception_global.reflector().get_jsobject().get(),
                 );
-                report_pending_exception(self.cx, true);
+                report_pending_exception(*self.cx, true);
             }
             drop(self.incumbent_script.take());
             drop(self.entry_script.take().unwrap());
diff --git a/components/script/dom/bindings/codegen/CodegenRust.py b/components/script/dom/bindings/codegen/CodegenRust.py
index ca041fdddeb..4bea65388b6 100644
--- a/components/script/dom/bindings/codegen/CodegenRust.py
+++ b/components/script/dom/bindings/codegen/CodegenRust.py
@@ -810,10 +810,10 @@ def getJSToNativeConversionInfo(type, descriptorProvider, failureCode=None,
                 if !JS_WrapValue(*cx, valueToResolve.handle_mut()) {
                 $*{exceptionCode}
                 }
-                match Promise::new_resolved(&promiseGlobal, *cx, valueToResolve.handle()) {
+                match Promise::new_resolved(&promiseGlobal, cx, valueToResolve.handle()) {
                     Ok(value) => value,
                     Err(error) => {
-                    throw_dom_exception(*cx, &promiseGlobal, error);
+                    throw_dom_exception(cx, &promiseGlobal, error);
                     $*{exceptionCode}
                     }
                 }
@@ -2588,8 +2588,7 @@ class CGConstructorEnabled(CGAbstractMethod):
         CGAbstractMethod.__init__(self, descriptor,
                                   'ConstructorEnabled', 'bool',
                                   [Argument("SafeJSContext", "aCx"),
-                                   Argument("HandleObject", "aObj")],
-                                  unsafe=True)
+                                   Argument("HandleObject", "aObj")])
 
     def definition_body(self):
         conditions = []
@@ -2651,8 +2650,8 @@ def InitUnforgeablePropertiesOnHolder(descriptor, properties):
     """
     unforgeables = []
 
-    defineUnforgeableAttrs = "define_guarded_properties(*cx, unforgeable_holder.handle(), %s, global);"
-    defineUnforgeableMethods = "define_guarded_methods(*cx, unforgeable_holder.handle(), %s, global);"
+    defineUnforgeableAttrs = "define_guarded_properties(cx, unforgeable_holder.handle(), %s, global);"
+    defineUnforgeableMethods = "define_guarded_methods(cx, unforgeable_holder.handle(), %s, global);"
 
     unforgeableMembers = [
         (defineUnforgeableAttrs, properties.unforgeable_attrs),
@@ -2762,7 +2761,7 @@ class CGWrapGlobalMethod(CGAbstractMethod):
             ("define_guarded_methods", self.properties.methods),
             ("define_guarded_constants", self.properties.consts)
         ]
-        members = ["%s(*cx, obj.handle(), %s, obj.handle());" % (function, array.variableName())
+        members = ["%s(cx, obj.handle(), %s, obj.handle());" % (function, array.variableName())
                    for (function, array) in pairs if array.length() > 0]
         values["members"] = "\n".join(members)
 
@@ -2772,7 +2771,7 @@ let _rt = RootedTraceable::new(&*raw);
 
 rooted!(in(*cx) let mut obj = ptr::null_mut::<JSObject>());
 create_global_object(
-    *cx,
+    cx,
     &Class.base,
     raw as *const libc::c_void,
     _trace,
@@ -2911,7 +2910,7 @@ class CGCreateInterfaceObjectsMethod(CGAbstractMethod):
 rooted!(in(*cx) let proto = %(proto)s);
 assert!(!proto.is_null());
 rooted!(in(*cx) let mut namespace = ptr::null_mut::<JSObject>());
-create_namespace_object(*cx, global, proto.handle(), &NAMESPACE_OBJECT_CLASS,
+create_namespace_object(cx, global, proto.handle(), &NAMESPACE_OBJECT_CLASS,
                         %(methods)s, %(name)s, namespace.handle_mut());
 assert!(!namespace.is_null());
 assert!((*cache)[PrototypeList::Constructor::%(id)s as usize].is_null());
@@ -2924,7 +2923,7 @@ assert!((*cache)[PrototypeList::Constructor::%(id)s as usize].is_null());
             assert not self.descriptor.interface.ctor() and self.descriptor.interface.hasConstants()
             return CGGeneric("""\
 rooted!(in(*cx) let mut interface = ptr::null_mut::<JSObject>());
-create_callback_interface_object(*cx, global, sConstants, %(name)s, interface.handle_mut());
+create_callback_interface_object(cx, global, sConstants, %(name)s, interface.handle_mut());
 assert!(!interface.is_null());
 assert!((*cache)[PrototypeList::Constructor::%(id)s as usize].is_null());
 (*cache)[PrototypeList::Constructor::%(id)s as usize] = interface.get();
@@ -2976,7 +2975,7 @@ assert!(!prototype_proto.is_null());""" % getPrototypeProto)]
 
         code.append(CGGeneric("""
 rooted!(in(*cx) let mut prototype = ptr::null_mut::<JSObject>());
-create_interface_prototype_object(*cx,
+create_interface_prototype_object(cx,
                                   global.into(),
                                   prototype_proto.handle().into(),
                                   &PrototypeClass,
@@ -3011,7 +3010,7 @@ assert!((*cache)[PrototypeList::ID::%(id)s as usize].is_null());
 assert!(!interface_proto.is_null());
 
 rooted!(in(*cx) let mut interface = ptr::null_mut::<JSObject>());
-create_noncallback_interface_object(*cx,
+create_noncallback_interface_object(cx,
                                     global.into(),
                                     interface_proto.handle(),
                                     &INTERFACE_OBJECT_CLASS,
@@ -3093,7 +3092,7 @@ assert!((*cache)[PrototypeList::Constructor::%(id)s as usize].is_null());
                 specs.append(CGGeneric("(%s as ConstructorClassHook, %s, %d)" % (hook, name, length)))
             values = CGIndenter(CGList(specs, "\n"), 4)
             code.append(CGWrapper(values, pre="%s = [\n" % decl, post="\n];"))
-            code.append(CGGeneric("create_named_constructors(*cx, global, &named_constructors, prototype.handle());"))
+            code.append(CGGeneric("create_named_constructors(cx, global, &named_constructors, prototype.handle());"))
 
         if self.descriptor.hasUnforgeableMembers:
             # We want to use the same JSClass and prototype as the object we'll
@@ -3137,23 +3136,25 @@ class CGGetPerInterfaceObject(CGAbstractMethod):
                 Argument('HandleObject', 'global'),
                 Argument('MutableHandleObject', 'mut rval')]
         CGAbstractMethod.__init__(self, descriptor, name,
-                                  'void', args, pub=pub, unsafe=True)
+                                  'void', args, pub=pub)
         self.id = idPrefix + "::" + MakeNativeName(self.descriptor.name)
 
     def definition_body(self):
         return CGGeneric("""
-assert!(((*get_object_class(global.get())).flags & JSCLASS_DOM_GLOBAL) != 0);
+unsafe {
+    assert!(((*get_object_class(global.get())).flags & JSCLASS_DOM_GLOBAL) != 0);
 
-/* Check to see whether the interface objects are already installed */
-let proto_or_iface_array = get_proto_or_iface_array(global.get());
-rval.set((*proto_or_iface_array)[%(id)s as usize]);
-if !rval.get().is_null() {
-    return;
+    /* Check to see whether the interface objects are already installed */
+    let proto_or_iface_array = get_proto_or_iface_array(global.get());
+    rval.set((*proto_or_iface_array)[%(id)s as usize]);
+    if !rval.get().is_null() {
+        return;
+    }
+
+    CreateInterfaceObjects(cx, global, proto_or_iface_array);
+    rval.set((*proto_or_iface_array)[%(id)s as usize]);
+    assert!(!rval.get().is_null());
 }
-
-CreateInterfaceObjects(cx, global, proto_or_iface_array);
-rval.set((*proto_or_iface_array)[%(id)s as usize]);
-assert!(!rval.get().is_null());
 """ % {"id": self.id})
 
 
@@ -3274,7 +3275,7 @@ class CGDefineDOMInterfaceMethod(CGAbstractMethod):
             Argument('HandleObject', 'global'),
         ]
         CGAbstractMethod.__init__(self, descriptor, 'DefineDOMInterface',
-                                  'void', args, pub=True, unsafe=True)
+                                  'void', args, pub=True)
 
     def define(self):
         return CGAbstractMethod.define(self)
@@ -3335,7 +3336,7 @@ class CGCallGenerator(CGThing):
         if "cx" not in argsPre and needsCx:
             args.prepend(CGGeneric("cx"))
         if nativeMethodName in descriptor.inCompartmentMethods:
-            args.append(CGGeneric("InCompartment::in_compartment(&AlreadyInCompartment::assert_for_cx(*cx))"))
+            args.append(CGGeneric("InCompartment::in_compartment(&AlreadyInCompartment::assert_for_cx(cx))"))
 
         # Build up our actual call
         self.cgRoot = CGList([], "\n")
@@ -3371,7 +3372,7 @@ class CGCallGenerator(CGThing):
                 "let result = match result {\n"
                 "    Ok(result) => result,\n"
                 "    Err(e) => {\n"
-                "        throw_dom_exception(*cx, %s, e);\n"
+                "        throw_dom_exception(cx, %s, e);\n"
                 "        return%s;\n"
                 "    },\n"
                 "};" % (glob, errorResult)))
@@ -5555,12 +5556,12 @@ let global = DomRoot::downcast::<dom::types::%s>(global).unwrap();
 // so we can do the spec's object-identity checks.
 rooted!(in(*cx) let new_target = UnwrapObjectDynamic(args.new_target().to_object(), *cx, 1));
 if new_target.is_null() {
-    throw_dom_exception(*cx, global.upcast::<GlobalScope>(), Error::Type("new.target is null".to_owned()));
+    throw_dom_exception(cx, global.upcast::<GlobalScope>(), Error::Type("new.target is null".to_owned()));
     return false;
 }
 
 if args.callee() == new_target.get() {
-    throw_dom_exception(*cx, global.upcast::<GlobalScope>(),
+    throw_dom_exception(cx, global.upcast::<GlobalScope>(),
         Error::Type("new.target must not be the active function object".to_owned()));
     return false;
 }
@@ -5601,7 +5602,7 @@ let result: Result<DomRoot<%s>, Error> = html_constructor(&global, &args);
 let result = match result {
     Ok(result) => result,
     Err(e) => {
-        throw_dom_exception(*cx, global.upcast::<GlobalScope>(), e);
+        throw_dom_exception(cx, global.upcast::<GlobalScope>(), e);
         return false;
     },
 };
@@ -6355,21 +6356,23 @@ class CGDictionary(CGThing):
         return string.Template(
             "impl ${selfName} {\n"
             "${empty}\n"
-            "    pub unsafe fn new(cx: SafeJSContext, val: HandleValue) \n"
+            "    pub fn new(cx: SafeJSContext, val: HandleValue) \n"
             "                      -> Result<ConversionResult<${actualType}>, ()> {\n"
-            "        let object = if val.get().is_null_or_undefined() {\n"
-            "            ptr::null_mut()\n"
-            "        } else if val.get().is_object() {\n"
-            "            val.get().to_object()\n"
-            "        } else {\n"
-            "            return Ok(ConversionResult::Failure(\"Value is not an object.\".into()));\n"
-            "        };\n"
-            "        rooted!(in(*cx) let object = object);\n"
+            "        unsafe {\n"
+            "            let object = if val.get().is_null_or_undefined() {\n"
+            "                ptr::null_mut()\n"
+            "            } else if val.get().is_object() {\n"
+            "                val.get().to_object()\n"
+            "            } else {\n"
+            "                return Ok(ConversionResult::Failure(\"Value is not an object.\".into()));\n"
+            "            };\n"
+            "            rooted!(in(*cx) let object = object);\n"
             "${preInitial}"
             "${initParent}"
             "${initMembers}"
             "${postInitial}"
-            "        Ok(ConversionResult::Success(dictionary))\n"
+            "            Ok(ConversionResult::Success(dictionary))\n"
+            "        }\n"
             "    }\n"
             "}\n"
             "\n"
@@ -6391,11 +6394,11 @@ class CGDictionary(CGThing):
                 "selfName": selfName,
                 "actualType": actualType,
                 "empty": CGIndenter(CGGeneric(self.makeEmpty()), indentLevel=4).define(),
-                "initParent": CGIndenter(CGGeneric(initParent), indentLevel=12).define(),
-                "initMembers": CGIndenter(memberInits, indentLevel=12).define(),
+                "initParent": CGIndenter(CGGeneric(initParent), indentLevel=16).define(),
+                "initMembers": CGIndenter(memberInits, indentLevel=16).define(),
                 "insertMembers": CGIndenter(memberInserts, indentLevel=8).define(),
-                "preInitial": CGIndenter(CGGeneric(preInitial), indentLevel=12).define(),
-                "postInitial": CGIndenter(CGGeneric(postInitial), indentLevel=12).define(),
+                "preInitial": CGIndenter(CGGeneric(preInitial), indentLevel=16).define(),
+                "postInitial": CGIndenter(CGGeneric(postInitial), indentLevel=16).define(),
             })
 
     def membersNeedTracing(self):
@@ -6825,8 +6828,8 @@ class CGCallback(CGClass):
         # Record the names of all the arguments, so we can use them when we call
         # the private method.
         argnames = [arg.name for arg in args]
-        argnamesWithThis = ["SafeJSContext::from_ptr(s.get_context())", "thisObjJS.handle()"] + argnames
-        argnamesWithoutThis = ["SafeJSContext::from_ptr(s.get_context())", "thisObjJS.handle()"] + argnames
+        argnamesWithThis = ["s.get_context()", "thisObjJS.handle()"] + argnames
+        argnamesWithoutThis = ["s.get_context()", "thisObjJS.handle()"] + argnames
         # Now that we've recorded the argnames for our call to our private
         # method, insert our optional argument for deciding whether the
         # CallSetup should re-throw exceptions on aRv.
@@ -6846,7 +6849,7 @@ class CGCallback(CGClass):
 
         bodyWithThis = string.Template(
             setupCall +
-            "rooted!(in(s.get_context()) let mut thisObjJS = ptr::null_mut::<JSObject>());\n"
+            "rooted!(in(*s.get_context()) let mut thisObjJS = ptr::null_mut::<JSObject>());\n"
             "wrap_call_this_object(s.get_context(), thisObj, thisObjJS.handle_mut());\n"
             "if thisObjJS.is_null() {\n"
             "    return Err(JSFailed);\n"
@@ -6857,7 +6860,7 @@ class CGCallback(CGClass):
             })
         bodyWithoutThis = string.Template(
             setupCall +
-            "rooted!(in(s.get_context()) let thisObjJS = ptr::null_mut::<JSObject>());\n"
+            "rooted!(in(*s.get_context()) let thisObjJS = ptr::null_mut::<JSObject>());\n"
             "unsafe { ${methodName}(${callArgs}) }").substitute({
                 "callArgs": ", ".join(argnamesWithoutThis),
                 "methodName": 'self.' + method.name,
@@ -7115,7 +7118,7 @@ class CallbackMember(CGNativeMember):
             return ""
         return (
             "CallSetup s(CallbackPreserveColor(), aRv, aExceptionHandling);\n"
-            "JSContext* cx = s.get_context();\n"
+            "JSContext* cx = *s.get_context();\n"
             "if (!cx) {\n"
             "    return Err(JSFailed);\n"
             "}\n")
@@ -7216,7 +7219,7 @@ class CallbackOperationBase(CallbackMethod):
             "methodName": self.methodName
         }
         getCallableFromProp = string.Template(
-            'r#try!(self.parent.get_callable_property(*cx, "${methodName}"))'
+            'r#try!(self.parent.get_callable_property(cx, "${methodName}"))'
         ).substitute(replacements)
         if not self.singleOperation:
             return 'rooted!(in(*cx) let callable =\n' + getCallableFromProp + ');\n'
diff --git a/components/script/dom/bindings/constant.rs b/components/script/dom/bindings/constant.rs
index 951b7f2a550..bce6e3d7844 100644
--- a/components/script/dom/bindings/constant.rs
+++ b/components/script/dom/bindings/constant.rs
@@ -4,8 +4,9 @@
 
 //! WebIDL constants.
 
+use crate::script_runtime::JSContext;
 use js::jsapi::JSPROP_READONLY;
-use js::jsapi::{JSContext, JSPROP_ENUMERATE, JSPROP_PERMANENT};
+use js::jsapi::{JSPROP_ENUMERATE, JSPROP_PERMANENT};
 use js::jsval::{BooleanValue, DoubleValue, Int32Value, JSVal, NullValue, UInt32Value};
 use js::rust::wrappers::JS_DefineProperty;
 use js::rust::HandleObject;
@@ -50,15 +51,17 @@ impl ConstantSpec {
 
 /// Defines constants on `obj`.
 /// Fails on JSAPI failure.
-pub unsafe fn define_constants(cx: *mut JSContext, obj: HandleObject, constants: &[ConstantSpec]) {
+pub fn define_constants(cx: JSContext, obj: HandleObject, constants: &[ConstantSpec]) {
     for spec in constants {
-        rooted!(in(cx) let value = spec.get_value());
-        assert!(JS_DefineProperty(
-            cx,
-            obj,
-            spec.name.as_ptr() as *const libc::c_char,
-            value.handle(),
-            (JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT) as u32
-        ));
+        rooted!(in(*cx) let value = spec.get_value());
+        unsafe {
+            assert!(JS_DefineProperty(
+                *cx,
+                obj,
+                spec.name.as_ptr() as *const libc::c_char,
+                value.handle(),
+                (JSPROP_ENUMERATE | JSPROP_READONLY | JSPROP_PERMANENT) as u32
+            ));
+        }
     }
 }
diff --git a/components/script/dom/bindings/error.rs b/components/script/dom/bindings/error.rs
index 40d690ff8d0..b0b6ca1f685 100644
--- a/components/script/dom/bindings/error.rs
+++ b/components/script/dom/bindings/error.rs
@@ -15,6 +15,7 @@ use crate::dom::bindings::conversions::{
 use crate::dom::bindings::str::USVString;
 use crate::dom::domexception::{DOMErrorName, DOMException};
 use crate::dom::globalscope::GlobalScope;
+use crate::script_runtime::JSContext as SafeJSContext;
 #[cfg(feature = "js_backtrace")]
 use backtrace::Backtrace;
 use js::error::{throw_range_error, throw_type_error};
@@ -104,10 +105,10 @@ pub type Fallible<T> = Result<T, Error>;
 pub type ErrorResult = Fallible<()>;
 
 /// Set a pending exception for the given `result` on `cx`.
-pub unsafe fn throw_dom_exception(cx: *mut JSContext, global: &GlobalScope, result: Error) {
+pub fn throw_dom_exception(cx: SafeJSContext, global: &GlobalScope, result: Error) {
     #[cfg(feature = "js_backtrace")]
     {
-        capture_stack!(in(cx) let stack);
+        capture_stack!(in(*cx) let stack);
         let js_stack = stack.and_then(|s| s.as_string(None));
         let rust_stack = Backtrace::new();
         LAST_EXCEPTION_BACKTRACE.with(|backtrace| {
@@ -139,27 +140,29 @@ pub unsafe fn throw_dom_exception(cx: *mut JSContext, global: &GlobalScope, resu
         Error::InvalidModification => DOMErrorName::InvalidModificationError,
         Error::NotReadable => DOMErrorName::NotReadableError,
         Error::Operation => DOMErrorName::OperationError,
-        Error::Type(message) => {
-            assert!(!JS_IsExceptionPending(cx));
-            throw_type_error(cx, &message);
+        Error::Type(message) => unsafe {
+            assert!(!JS_IsExceptionPending(*cx));
+            throw_type_error(*cx, &message);
             return;
         },
-        Error::Range(message) => {
-            assert!(!JS_IsExceptionPending(cx));
-            throw_range_error(cx, &message);
+        Error::Range(message) => unsafe {
+            assert!(!JS_IsExceptionPending(*cx));
+            throw_range_error(*cx, &message);
             return;
         },
-        Error::JSFailed => {
-            assert!(JS_IsExceptionPending(cx));
+        Error::JSFailed => unsafe {
+            assert!(JS_IsExceptionPending(*cx));
             return;
         },
     };
 
-    assert!(!JS_IsExceptionPending(cx));
-    let exception = DOMException::new(global, code);
-    rooted!(in(cx) let mut thrown = UndefinedValue());
-    exception.to_jsval(cx, thrown.handle_mut());
-    JS_SetPendingException(cx, thrown.handle());
+    unsafe {
+        assert!(!JS_IsExceptionPending(*cx));
+        let exception = DOMException::new(global, code);
+        rooted!(in(*cx) let mut thrown = UndefinedValue());
+        exception.to_jsval(*cx, thrown.handle_mut());
+        JS_SetPendingException(*cx, thrown.handle());
+    }
 }
 
 /// A struct encapsulating information about a runtime script error.
@@ -310,7 +313,7 @@ impl Error {
             Error::JSFailed => (),
             _ => assert!(!JS_IsExceptionPending(cx)),
         }
-        throw_dom_exception(cx, global, self);
+        throw_dom_exception(SafeJSContext::from_ptr(cx), global, self);
         assert!(JS_IsExceptionPending(cx));
         assert!(JS_GetPendingException(cx, rval));
         JS_ClearPendingException(cx);
diff --git a/components/script/dom/bindings/guard.rs b/components/script/dom/bindings/guard.rs
index 40052c7098e..bba30e1581c 100644
--- a/components/script/dom/bindings/guard.rs
+++ b/components/script/dom/bindings/guard.rs
@@ -6,7 +6,7 @@
 
 use crate::dom::bindings::codegen::InterfaceObjectMap;
 use crate::dom::bindings::interface::is_exposed_in;
-use js::jsapi::JSContext;
+use crate::script_runtime::JSContext;
 use js::rust::HandleObject;
 use servo_config::prefs;
 
@@ -28,12 +28,7 @@ impl<T: Clone + Copy> Guard<T> {
     /// Expose the value if the condition is satisfied.
     ///
     /// The passed handle is the object on which the value may be exposed.
-    pub unsafe fn expose(
-        &self,
-        cx: *mut JSContext,
-        obj: HandleObject,
-        global: HandleObject,
-    ) -> Option<T> {
+    pub fn expose(&self, cx: JSContext, obj: HandleObject, global: HandleObject) -> Option<T> {
         if self.condition.is_satisfied(cx, obj, global) {
             Some(self.value)
         } else {
@@ -45,7 +40,7 @@ impl<T: Clone + Copy> Guard<T> {
 /// A condition to expose things.
 pub enum Condition {
     /// The condition is satisfied if the function returns true.
-    Func(unsafe fn(*mut JSContext, HandleObject) -> bool),
+    Func(fn(JSContext, HandleObject) -> bool),
     /// The condition is satisfied if the preference is set.
     Pref(&'static str),
     // The condition is satisfied if the interface is exposed in the global.
@@ -55,12 +50,7 @@ pub enum Condition {
 }
 
 impl Condition {
-    unsafe fn is_satisfied(
-        &self,
-        cx: *mut JSContext,
-        obj: HandleObject,
-        global: HandleObject,
-    ) -> bool {
+    fn is_satisfied(&self, cx: JSContext, obj: HandleObject, global: HandleObject) -> bool {
         match *self {
             Condition::Pref(name) => prefs::pref_map().get(name).as_bool().unwrap_or(false),
             Condition::Func(f) => f(cx, obj),
diff --git a/components/script/dom/bindings/htmlconstructor.rs b/components/script/dom/bindings/htmlconstructor.rs
index 6faa4f6211c..1937f400fda 100644
--- a/components/script/dom/bindings/htmlconstructor.rs
+++ b/components/script/dom/bindings/htmlconstructor.rs
@@ -76,13 +76,13 @@ use crate::dom::customelementregistry::{ConstructionStackEntry, CustomElementSta
 use crate::dom::element::{Element, ElementCreator};
 use crate::dom::htmlelement::HTMLElement;
 use crate::dom::window::Window;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use crate::script_thread::ScriptThread;
 use html5ever::interface::QualName;
 use html5ever::LocalName;
 use js::glue::UnwrapObjectStatic;
 use js::jsapi::{CallArgs, CurrentGlobalOrNull};
-use js::jsapi::{JSAutoRealm, JSContext, JSObject};
+use js::jsapi::{JSAutoRealm, JSObject};
 use js::rust::HandleObject;
 use js::rust::MutableHandleObject;
 use std::ptr;
@@ -134,7 +134,7 @@ where
             // Step 5
             get_constructor_object_from_local_name(
                 definition.local_name.clone(),
-                *window.get_cx(),
+                window.get_cx(),
                 global_object.handle(),
                 constructor.handle_mut(),
             );
@@ -196,13 +196,13 @@ where
 /// This list should only include elements marked with the [HTMLConstructor] extended attribute.
 pub fn get_constructor_object_from_local_name(
     name: LocalName,
-    cx: *mut JSContext,
+    cx: JSContext,
     global: HandleObject,
     rval: MutableHandleObject,
 ) -> bool {
     macro_rules! get_constructor(
         ($binding:ident) => ({
-            unsafe { $binding::GetConstructorObject(SafeJSContext::from_ptr(cx), global, rval); }
+            $binding::GetConstructorObject(cx, global, rval);
             true
         })
     );
diff --git a/components/script/dom/bindings/interface.rs b/components/script/dom/bindings/interface.rs
index 6f2183339af..0a5ee24fb23 100644
--- a/components/script/dom/bindings/interface.rs
+++ b/components/script/dom/bindings/interface.rs
@@ -12,6 +12,7 @@ use crate::dom::bindings::guard::Guard;
 use crate::dom::bindings::utils::{
     get_proto_or_iface_array, ProtoOrIfaceArray, DOM_PROTOTYPE_SLOT,
 };
+use crate::script_runtime::JSContext as SafeJSContext;
 use js::error::throw_type_error;
 use js::glue::UncheckedUnwrapObject;
 use js::jsapi::HandleObject as RawHandleObject;
@@ -129,7 +130,7 @@ pub type TraceHook = unsafe extern "C" fn(trc: *mut JSTracer, obj: *mut JSObject
 
 /// Create a global object with the given class.
 pub unsafe fn create_global_object(
-    cx: *mut JSContext,
+    cx: SafeJSContext,
     class: &'static JSClass,
     private: *const libc::c_void,
     trace: TraceHook,
@@ -142,7 +143,7 @@ pub unsafe fn create_global_object(
     options.creationOptions_.sharedMemoryAndAtomics_ = true;
 
     rval.set(JS_NewGlobalObject(
-        cx,
+        *cx,
         class,
         ptr::null_mut(),
         OnNewGlobalHookOption::DontFireOnNewGlobalHook,
@@ -159,20 +160,22 @@ pub unsafe fn create_global_object(
     let val = PrivateValue(Box::into_raw(proto_array) as *const libc::c_void);
     JS_SetReservedSlot(rval.get(), DOM_PROTOTYPE_SLOT, &val);
 
-    let _ac = JSAutoRealm::new(cx, rval.get());
-    JS_FireOnNewGlobalObject(cx, rval.handle());
+    let _ac = JSAutoRealm::new(*cx, rval.get());
+    JS_FireOnNewGlobalObject(*cx, rval.handle());
 }
 
 /// Create and define the interface object of a callback interface.
-pub unsafe fn create_callback_interface_object(
-    cx: *mut JSContext,
+pub fn create_callback_interface_object(
+    cx: SafeJSContext,
     global: HandleObject,
     constants: &[Guard<&[ConstantSpec]>],
     name: &[u8],
     mut rval: MutableHandleObject,
 ) {
     assert!(!constants.is_empty());
-    rval.set(JS_NewObject(cx, ptr::null()));
+    unsafe {
+        rval.set(JS_NewObject(*cx, ptr::null()));
+    }
     assert!(!rval.is_null());
     define_guarded_constants(cx, rval.handle(), constants, global);
     define_name(cx, rval.handle(), name);
@@ -180,8 +183,8 @@ pub unsafe fn create_callback_interface_object(
 }
 
 /// Create the interface prototype object of a non-callback interface.
-pub unsafe fn create_interface_prototype_object(
-    cx: *mut JSContext,
+pub fn create_interface_prototype_object(
+    cx: SafeJSContext,
     global: HandleObject,
     proto: HandleObject,
     class: &'static JSClass,
@@ -203,27 +206,29 @@ pub unsafe fn create_interface_prototype_object(
     );
 
     if !unscopable_names.is_empty() {
-        rooted!(in(cx) let mut unscopable_obj = ptr::null_mut::<JSObject>());
+        rooted!(in(*cx) let mut unscopable_obj = ptr::null_mut::<JSObject>());
         create_unscopable_object(cx, unscopable_names, unscopable_obj.handle_mut());
+        unsafe {
+            let unscopable_symbol = GetWellKnownSymbol(*cx, SymbolCode::unscopables);
+            assert!(!unscopable_symbol.is_null());
 
-        let unscopable_symbol = GetWellKnownSymbol(cx, SymbolCode::unscopables);
-        assert!(!unscopable_symbol.is_null());
+            rooted!(in(*cx) let mut unscopable_id: jsid);
+            RUST_SYMBOL_TO_JSID(unscopable_symbol, unscopable_id.handle_mut());
 
-        rooted!(in(cx) let mut unscopable_id: jsid);
-        RUST_SYMBOL_TO_JSID(unscopable_symbol, unscopable_id.handle_mut());
-        assert!(JS_DefinePropertyById5(
-            cx,
-            rval.handle(),
-            unscopable_id.handle(),
-            unscopable_obj.handle(),
-            JSPROP_READONLY as u32
-        ))
+            assert!(JS_DefinePropertyById5(
+                *cx,
+                rval.handle(),
+                unscopable_id.handle(),
+                unscopable_obj.handle(),
+                JSPROP_READONLY as u32
+            ))
+        }
     }
 }
 
 /// Create and define the interface object of a non-callback interface.
-pub unsafe fn create_noncallback_interface_object(
-    cx: *mut JSContext,
+pub fn create_noncallback_interface_object(
+    cx: SafeJSContext,
     global: HandleObject,
     proto: HandleObject,
     class: &'static NonCallbackInterfaceObjectClass,
@@ -245,54 +250,58 @@ pub unsafe fn create_noncallback_interface_object(
         constants,
         rval,
     );
-    assert!(JS_LinkConstructorAndPrototype(
-        cx,
-        rval.handle(),
-        interface_prototype_object
-    ));
+    unsafe {
+        assert!(JS_LinkConstructorAndPrototype(
+            *cx,
+            rval.handle(),
+            interface_prototype_object
+        ));
+    }
     define_name(cx, rval.handle(), name);
     define_length(cx, rval.handle(), i32::try_from(length).expect("overflow"));
     define_on_global_object(cx, global, name, rval.handle());
 }
 
 /// Create and define the named constructors of a non-callback interface.
-pub unsafe fn create_named_constructors(
-    cx: *mut JSContext,
+pub fn create_named_constructors(
+    cx: SafeJSContext,
     global: HandleObject,
     named_constructors: &[(ConstructorClassHook, &[u8], u32)],
     interface_prototype_object: HandleObject,
 ) {
-    rooted!(in(cx) let mut constructor = ptr::null_mut::<JSObject>());
+    rooted!(in(*cx) let mut constructor = ptr::null_mut::<JSObject>());
 
     for &(native, name, arity) in named_constructors {
         assert_eq!(*name.last().unwrap(), b'\0');
 
-        let fun = JS_NewFunction(
-            cx,
-            Some(native),
-            arity,
-            JSFUN_CONSTRUCTOR,
-            name.as_ptr() as *const libc::c_char,
-        );
-        assert!(!fun.is_null());
-        constructor.set(JS_GetFunctionObject(fun));
-        assert!(!constructor.is_null());
+        unsafe {
+            let fun = JS_NewFunction(
+                *cx,
+                Some(native),
+                arity,
+                JSFUN_CONSTRUCTOR,
+                name.as_ptr() as *const libc::c_char,
+            );
+            assert!(!fun.is_null());
+            constructor.set(JS_GetFunctionObject(fun));
+            assert!(!constructor.is_null());
 
-        assert!(JS_DefineProperty3(
-            cx,
-            constructor.handle(),
-            b"prototype\0".as_ptr() as *const libc::c_char,
-            interface_prototype_object,
-            (JSPROP_PERMANENT | JSPROP_READONLY) as u32
-        ));
+            assert!(JS_DefineProperty3(
+                *cx,
+                constructor.handle(),
+                b"prototype\0".as_ptr() as *const libc::c_char,
+                interface_prototype_object,
+                (JSPROP_PERMANENT | JSPROP_READONLY) as u32
+            ));
+        }
 
         define_on_global_object(cx, global, name, constructor.handle());
     }
 }
 
 /// Create a new object with a unique type.
-pub unsafe fn create_object(
-    cx: *mut JSContext,
+pub fn create_object(
+    cx: SafeJSContext,
     global: HandleObject,
     proto: HandleObject,
     class: &'static JSClass,
@@ -301,7 +310,9 @@ pub unsafe fn create_object(
     constants: &[Guard<&[ConstantSpec]>],
     mut rval: MutableHandleObject,
 ) {
-    rval.set(JS_NewObjectWithUniqueType(cx, class, proto));
+    unsafe {
+        rval.set(JS_NewObjectWithUniqueType(*cx, class, proto));
+    }
     assert!(!rval.is_null());
     define_guarded_methods(cx, rval.handle(), methods, global);
     define_guarded_properties(cx, rval.handle(), properties, global);
@@ -309,8 +320,8 @@ pub unsafe fn create_object(
 }
 
 /// Conditionally define constants on an object.
-pub unsafe fn define_guarded_constants(
-    cx: *mut JSContext,
+pub fn define_guarded_constants(
+    cx: SafeJSContext,
     obj: HandleObject,
     constants: &[Guard<&[ConstantSpec]>],
     global: HandleObject,
@@ -323,57 +334,65 @@ pub unsafe fn define_guarded_constants(
 }
 
 /// Conditionally define methods on an object.
-pub unsafe fn define_guarded_methods(
-    cx: *mut JSContext,
+pub fn define_guarded_methods(
+    cx: SafeJSContext,
     obj: HandleObject,
     methods: &[Guard<&'static [JSFunctionSpec]>],
     global: HandleObject,
 ) {
     for guard in methods {
         if let Some(specs) = guard.expose(cx, obj, global) {
-            define_methods(cx, obj, specs).unwrap();
+            unsafe {
+                define_methods(*cx, obj, specs).unwrap();
+            }
         }
     }
 }
 
 /// Conditionally define properties on an object.
-pub unsafe fn define_guarded_properties(
-    cx: *mut JSContext,
+pub fn define_guarded_properties(
+    cx: SafeJSContext,
     obj: HandleObject,
     properties: &[Guard<&'static [JSPropertySpec]>],
     global: HandleObject,
 ) {
     for guard in properties {
         if let Some(specs) = guard.expose(cx, obj, global) {
-            define_properties(cx, obj, specs).unwrap();
+            unsafe {
+                define_properties(*cx, obj, specs).unwrap();
+            }
         }
     }
 }
 
 /// Returns whether an interface with exposure set given by `globals` should
 /// be exposed in the global object `obj`.
-pub unsafe fn is_exposed_in(object: HandleObject, globals: Globals) -> bool {
-    let unwrapped = UncheckedUnwrapObject(object.get(), /* stopAtWindowProxy = */ 0);
-    let dom_class = get_dom_class(unwrapped).unwrap();
-    globals.contains(dom_class.global)
+pub fn is_exposed_in(object: HandleObject, globals: Globals) -> bool {
+    unsafe {
+        let unwrapped = UncheckedUnwrapObject(object.get(), /* stopAtWindowProxy = */ 0);
+        let dom_class = get_dom_class(unwrapped).unwrap();
+        globals.contains(dom_class.global)
+    }
 }
 
 /// Define a property with a given name on the global object. Should be called
 /// through the resolve hook.
-pub unsafe fn define_on_global_object(
-    cx: *mut JSContext,
+pub fn define_on_global_object(
+    cx: SafeJSContext,
     global: HandleObject,
     name: &[u8],
     obj: HandleObject,
 ) {
     assert_eq!(*name.last().unwrap(), b'\0');
-    assert!(JS_DefineProperty3(
-        cx,
-        global,
-        name.as_ptr() as *const libc::c_char,
-        obj,
-        JSPROP_RESOLVING
-    ));
+    unsafe {
+        assert!(JS_DefineProperty3(
+            *cx,
+            global,
+            name.as_ptr() as *const libc::c_char,
+            obj,
+            JSPROP_RESOLVING
+        ));
+    }
 }
 
 const OBJECT_OPS: ObjectOps = ObjectOps {
@@ -409,6 +428,7 @@ unsafe extern "C" fn has_instance_hook(
     value: RawMutableHandleValue,
     rval: *mut bool,
 ) -> bool {
+    let cx = SafeJSContext::from_ptr(cx);
     let obj_raw = HandleObject::from_raw(obj);
     let val_raw = HandleValue::from_raw(value.handle());
     match has_instance(cx, obj_raw, val_raw) {
@@ -422,8 +442,8 @@ unsafe extern "C" fn has_instance_hook(
 
 /// Return whether a value is an instance of a given prototype.
 /// <http://heycam.github.io/webidl/#es-interface-hasinstance>
-unsafe fn has_instance(
-    cx: *mut JSContext,
+fn has_instance(
+    cx: SafeJSContext,
     interface_object: HandleObject,
     value: HandleValue,
 ) -> Result<bool, ()> {
@@ -432,86 +452,91 @@ unsafe fn has_instance(
         return Ok(false);
     }
 
-    rooted!(in(cx) let mut value_out = value.to_object());
-    rooted!(in(cx) let mut value = value.to_object());
+    rooted!(in(*cx) let mut value_out = value.to_object());
+    rooted!(in(*cx) let mut value = value.to_object());
 
-    let js_class = get_object_class(interface_object.get());
-    let object_class = &*(js_class as *const NonCallbackInterfaceObjectClass);
+    unsafe {
+        let js_class = get_object_class(interface_object.get());
+        let object_class = &*(js_class as *const NonCallbackInterfaceObjectClass);
 
-    if let Ok(dom_class) = get_dom_class(UncheckedUnwrapObject(
-        value.get(),
-        /* stopAtWindowProxy = */ 0,
-    )) {
-        if dom_class.interface_chain[object_class.proto_depth as usize] == object_class.proto_id {
-            // Step 4.
-            return Ok(true);
+        if let Ok(dom_class) = get_dom_class(UncheckedUnwrapObject(
+            value.get(),
+            /* stopAtWindowProxy = */ 0,
+        )) {
+            if dom_class.interface_chain[object_class.proto_depth as usize] == object_class.proto_id
+            {
+                // Step 4.
+                return Ok(true);
+            }
         }
-    }
 
-    // Step 2.
-    let global = GetNonCCWObjectGlobal(interface_object.get());
-    assert!(!global.is_null());
-    let proto_or_iface_array = get_proto_or_iface_array(global);
-    rooted!(in(cx) let prototype = (*proto_or_iface_array)[object_class.proto_id as usize]);
-    assert!(!prototype.is_null());
-    // Step 3 only concern legacy callback interface objects (i.e. NodeFilter).
+        // Step 2.
+        let global = GetNonCCWObjectGlobal(interface_object.get());
+        assert!(!global.is_null());
+        let proto_or_iface_array = get_proto_or_iface_array(global);
+        rooted!(in(*cx) let prototype = (*proto_or_iface_array)[object_class.proto_id as usize]);
+        assert!(!prototype.is_null());
+        // Step 3 only concern legacy callback interface objects (i.e. NodeFilter).
 
-    while JS_GetPrototype(cx, value.handle(), value_out.handle_mut()) {
-        *value = *value_out;
-        if value.is_null() {
-            // Step 5.2.
-            return Ok(false);
-        } else if value.get() as *const _ == prototype.get() {
-            // Step 5.3.
-            return Ok(true);
+        while JS_GetPrototype(*cx, value.handle(), value_out.handle_mut()) {
+            *value = *value_out;
+            if value.is_null() {
+                // Step 5.2.
+                return Ok(false);
+            } else if value.get() as *const _ == prototype.get() {
+                // Step 5.3.
+                return Ok(true);
+            }
         }
     }
     // JS_GetPrototype threw an exception.
     Err(())
 }
 
-unsafe fn create_unscopable_object(
-    cx: *mut JSContext,
-    names: &[&[u8]],
-    mut rval: MutableHandleObject,
-) {
+fn create_unscopable_object(cx: SafeJSContext, names: &[&[u8]], mut rval: MutableHandleObject) {
     assert!(!names.is_empty());
     assert!(rval.is_null());
-    rval.set(JS_NewPlainObject(cx));
-    assert!(!rval.is_null());
-    for &name in names {
-        assert_eq!(*name.last().unwrap(), b'\0');
-        assert!(JS_DefineProperty(
-            cx,
-            rval.handle(),
-            name.as_ptr() as *const libc::c_char,
-            HandleValue::from_raw(TrueHandleValue),
-            JSPROP_READONLY as u32,
+    unsafe {
+        rval.set(JS_NewPlainObject(*cx));
+        assert!(!rval.is_null());
+        for &name in names {
+            assert_eq!(*name.last().unwrap(), b'\0');
+            assert!(JS_DefineProperty(
+                *cx,
+                rval.handle(),
+                name.as_ptr() as *const libc::c_char,
+                HandleValue::from_raw(TrueHandleValue),
+                JSPROP_READONLY as u32,
+            ));
+        }
+    }
+}
+
+fn define_name(cx: SafeJSContext, obj: HandleObject, name: &[u8]) {
+    assert_eq!(*name.last().unwrap(), b'\0');
+    unsafe {
+        rooted!(in(*cx) let name = JS_AtomizeAndPinString(*cx, name.as_ptr() as *const libc::c_char));
+        assert!(!name.is_null());
+        assert!(JS_DefineProperty4(
+            *cx,
+            obj,
+            b"name\0".as_ptr() as *const libc::c_char,
+            name.handle().into(),
+            JSPROP_READONLY as u32
         ));
     }
 }
 
-unsafe fn define_name(cx: *mut JSContext, obj: HandleObject, name: &[u8]) {
-    assert_eq!(*name.last().unwrap(), b'\0');
-    rooted!(in(cx) let name = JS_AtomizeAndPinString(cx, name.as_ptr() as *const libc::c_char));
-    assert!(!name.is_null());
-    assert!(JS_DefineProperty4(
-        cx,
-        obj,
-        b"name\0".as_ptr() as *const libc::c_char,
-        name.handle().into(),
-        JSPROP_READONLY as u32
-    ));
-}
-
-unsafe fn define_length(cx: *mut JSContext, obj: HandleObject, length: i32) {
-    assert!(JS_DefineProperty5(
-        cx,
-        obj,
-        b"length\0".as_ptr() as *const libc::c_char,
-        length,
-        JSPROP_READONLY as u32
-    ));
+fn define_length(cx: SafeJSContext, obj: HandleObject, length: i32) {
+    unsafe {
+        assert!(JS_DefineProperty5(
+            *cx,
+            obj,
+            b"length\0".as_ptr() as *const libc::c_char,
+            length,
+            JSPROP_READONLY as u32
+        ));
+    }
 }
 
 unsafe extern "C" fn invalid_constructor(
diff --git a/components/script/dom/bindings/iterable.rs b/components/script/dom/bindings/iterable.rs
index 5ee790cf2d3..17c5f2fb1ae 100644
--- a/components/script/dom/bindings/iterable.rs
+++ b/components/script/dom/bindings/iterable.rs
@@ -13,10 +13,10 @@ use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
 use crate::dom::bindings::root::{Dom, DomRoot};
 use crate::dom::bindings::trace::{JSTraceable, RootedTraceableBox};
 use crate::dom::globalscope::GlobalScope;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use dom_struct::dom_struct;
 use js::conversions::ToJSValConvertible;
-use js::jsapi::{Heap, JSContext, JSObject};
+use js::jsapi::{Heap, JSObject};
 use js::jsval::UndefinedValue;
 use js::rust::{HandleValue, MutableHandleObject};
 use std::cell::Cell;
@@ -63,7 +63,7 @@ impl<T: DomObject + JSTraceable + Iterable> IterableIterator<T> {
     pub fn new(
         iterable: &T,
         type_: IteratorType,
-        wrap: unsafe fn(SafeJSContext, &GlobalScope, Box<IterableIterator<T>>) -> DomRoot<Self>,
+        wrap: unsafe fn(JSContext, &GlobalScope, Box<IterableIterator<T>>) -> DomRoot<Self>,
     ) -> DomRoot<Self> {
         let iterator = Box::new(IterableIterator {
             reflector: Reflector::new(),
@@ -76,12 +76,12 @@ impl<T: DomObject + JSTraceable + Iterable> IterableIterator<T> {
 
     /// Return the next value from the iterable object.
     #[allow(non_snake_case)]
-    pub fn Next(&self, cx: SafeJSContext) -> Fallible<NonNull<JSObject>> {
+    pub fn Next(&self, cx: JSContext) -> Fallible<NonNull<JSObject>> {
         let index = self.index.get();
         rooted!(in(*cx) let mut value = UndefinedValue());
         rooted!(in(*cx) let mut rval = ptr::null_mut::<JSObject>());
         let result = if index >= self.iterable.get_iterable_length() {
-            dict_return(*cx, rval.handle_mut(), true, value.handle())
+            dict_return(cx, rval.handle_mut(), true, value.handle())
         } else {
             match self.type_ {
                 IteratorType::Keys => {
@@ -90,7 +90,7 @@ impl<T: DomObject + JSTraceable + Iterable> IterableIterator<T> {
                             .get_key_at_index(index)
                             .to_jsval(*cx, value.handle_mut());
                     }
-                    dict_return(*cx, rval.handle_mut(), false, value.handle())
+                    dict_return(cx, rval.handle_mut(), false, value.handle())
                 },
                 IteratorType::Values => {
                     unsafe {
@@ -98,7 +98,7 @@ impl<T: DomObject + JSTraceable + Iterable> IterableIterator<T> {
                             .get_value_at_index(index)
                             .to_jsval(*cx, value.handle_mut());
                     }
-                    dict_return(*cx, rval.handle_mut(), false, value.handle())
+                    dict_return(cx, rval.handle_mut(), false, value.handle())
                 },
                 IteratorType::Entries => {
                     rooted!(in(*cx) let mut key = UndefinedValue());
@@ -110,7 +110,7 @@ impl<T: DomObject + JSTraceable + Iterable> IterableIterator<T> {
                             .get_value_at_index(index)
                             .to_jsval(*cx, value.handle_mut());
                     }
-                    key_and_value_return(*cx, rval.handle_mut(), key.handle(), value.handle())
+                    key_and_value_return(cx, rval.handle_mut(), key.handle(), value.handle())
                 },
             }
         };
@@ -120,7 +120,7 @@ impl<T: DomObject + JSTraceable + Iterable> IterableIterator<T> {
 }
 
 fn dict_return(
-    cx: *mut JSContext,
+    cx: JSContext,
     mut result: MutableHandleObject,
     done: bool,
     value: HandleValue,
@@ -128,16 +128,16 @@ fn dict_return(
     let mut dict = IterableKeyOrValueResult::empty();
     dict.done = done;
     dict.value.set(value.get());
-    rooted!(in(cx) let mut dict_value = UndefinedValue());
+    rooted!(in(*cx) let mut dict_value = UndefinedValue());
     unsafe {
-        dict.to_jsval(cx, dict_value.handle_mut());
+        dict.to_jsval(*cx, dict_value.handle_mut());
     }
     result.set(dict_value.to_object());
     Ok(())
 }
 
 fn key_and_value_return(
-    cx: *mut JSContext,
+    cx: JSContext,
     mut result: MutableHandleObject,
     key: HandleValue,
     value: HandleValue,
@@ -150,9 +150,9 @@ fn key_and_value_return(
             .map(|handle| RootedTraceableBox::from_box(Heap::boxed(handle.get())))
             .collect(),
     );
-    rooted!(in(cx) let mut dict_value = UndefinedValue());
+    rooted!(in(*cx) let mut dict_value = UndefinedValue());
     unsafe {
-        dict.to_jsval(cx, dict_value.handle_mut());
+        dict.to_jsval(*cx, dict_value.handle_mut());
     }
     result.set(dict_value.to_object());
     Ok(())
diff --git a/components/script/dom/bindings/namespace.rs b/components/script/dom/bindings/namespace.rs
index a6539c83de6..82b7bd8834e 100644
--- a/components/script/dom/bindings/namespace.rs
+++ b/components/script/dom/bindings/namespace.rs
@@ -6,7 +6,8 @@
 
 use crate::dom::bindings::guard::Guard;
 use crate::dom::bindings::interface::{create_object, define_on_global_object};
-use js::jsapi::{JSClass, JSContext, JSFunctionSpec};
+use crate::script_runtime::JSContext;
+use js::jsapi::{JSClass, JSFunctionSpec};
 use js::rust::{HandleObject, MutableHandleObject};
 
 /// The class of a namespace object.
@@ -28,8 +29,8 @@ impl NamespaceObjectClass {
 }
 
 /// Create a new namespace object.
-pub unsafe fn create_namespace_object(
-    cx: *mut JSContext,
+pub fn create_namespace_object(
+    cx: JSContext,
     global: HandleObject,
     proto: HandleObject,
     class: &'static NamespaceObjectClass,
diff --git a/components/script/dom/bluetooth.rs b/components/script/dom/bluetooth.rs
index 4a5a9af9c43..989bcce27b7 100644
--- a/components/script/dom/bluetooth.rs
+++ b/components/script/dom/bluetooth.rs
@@ -30,13 +30,13 @@ use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::permissions::{get_descriptor_permission_state, PermissionAlgorithm};
 use crate::dom::promise::Promise;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use crate::task::TaskOnce;
 use dom_struct::dom_struct;
 use ipc_channel::ipc::{self, IpcSender};
 use ipc_channel::router::ROUTER;
 use js::conversions::ConversionResult;
-use js::jsapi::{JSContext, JSObject};
+use js::jsapi::JSObject;
 use js::jsval::{ObjectValue, UndefinedValue};
 use profile_traits::ipc as ProfiledIpc;
 use std::cell::Ref;
@@ -616,28 +616,24 @@ impl PermissionAlgorithm for Bluetooth {
     type Descriptor = BluetoothPermissionDescriptor;
     type Status = BluetoothPermissionResult;
 
-    #[allow(unsafe_code)]
     fn create_descriptor(
-        cx: *mut JSContext,
+        cx: JSContext,
         permission_descriptor_obj: *mut JSObject,
     ) -> Result<BluetoothPermissionDescriptor, Error> {
-        rooted!(in(cx) let mut property = UndefinedValue());
+        rooted!(in(*cx) let mut property = UndefinedValue());
         property
             .handle_mut()
             .set(ObjectValue(permission_descriptor_obj));
-        unsafe {
-            match BluetoothPermissionDescriptor::new(SafeJSContext::from_ptr(cx), property.handle())
-            {
-                Ok(ConversionResult::Success(descriptor)) => Ok(descriptor),
-                Ok(ConversionResult::Failure(error)) => Err(Error::Type(error.into_owned())),
-                Err(_) => Err(Error::Type(String::from(BT_DESC_CONVERSION_ERROR))),
-            }
+        match BluetoothPermissionDescriptor::new(cx, property.handle()) {
+            Ok(ConversionResult::Success(descriptor)) => Ok(descriptor),
+            Ok(ConversionResult::Failure(error)) => Err(Error::Type(error.into_owned())),
+            Err(_) => Err(Error::Type(String::from(BT_DESC_CONVERSION_ERROR))),
         }
     }
 
     // https://webbluetoothcg.github.io/web-bluetooth/#query-the-bluetooth-permission
     fn permission_query(
-        _cx: *mut JSContext,
+        _cx: JSContext,
         promise: &Rc<Promise>,
         descriptor: &BluetoothPermissionDescriptor,
         status: &BluetoothPermissionResult,
@@ -727,7 +723,7 @@ impl PermissionAlgorithm for Bluetooth {
 
     // https://webbluetoothcg.github.io/web-bluetooth/#request-the-bluetooth-permission
     fn permission_request(
-        _cx: *mut JSContext,
+        _cx: JSContext,
         promise: &Rc<Promise>,
         descriptor: &BluetoothPermissionDescriptor,
         status: &BluetoothPermissionResult,
diff --git a/components/script/dom/create.rs b/components/script/dom/create.rs
index 18c9504a245..e992a8707dd 100644
--- a/components/script/dom/create.rs
+++ b/components/script/dom/create.rs
@@ -158,7 +158,7 @@ fn create_html_element(
                             unsafe {
                                 let _ac =
                                     JSAutoRealm::new(*cx, global.reflector().get_jsobject().get());
-                                throw_dom_exception(*cx, &global, error);
+                                throw_dom_exception(cx, &global, error);
                                 report_pending_exception(*cx, true);
                             }
 
diff --git a/components/script/dom/customelementregistry.rs b/components/script/dom/customelementregistry.rs
index 2603768ed83..64117959500 100644
--- a/components/script/dom/customelementregistry.rs
+++ b/components/script/dom/customelementregistry.rs
@@ -31,14 +31,14 @@ use crate::dom::node::{document_from_node, window_from_node, Node, ShadowIncludi
 use crate::dom::promise::Promise;
 use crate::dom::window::Window;
 use crate::microtask::Microtask;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use crate::script_thread::ScriptThread;
 use dom_struct::dom_struct;
 use html5ever::{LocalName, Namespace, Prefix};
 use js::conversions::ToJSValConvertible;
 use js::glue::UnwrapObjectStatic;
 use js::jsapi::{HandleValueArray, Heap, IsCallable, IsConstructor};
-use js::jsapi::{JSAutoRealm, JSContext, JSObject};
+use js::jsapi::{JSAutoRealm, JSObject};
 use js::jsval::{JSVal, NullValue, ObjectValue, UndefinedValue};
 use js::rust::wrappers::{Construct1, JS_GetProperty, SameValue};
 use js::rust::{HandleObject, HandleValue, MutableHandleValue};
@@ -171,14 +171,10 @@ impl CustomElementRegistry {
 
         // Step 4
         Ok(LifecycleCallbacks {
-            connected_callback: get_callback(*cx, prototype, b"connectedCallback\0")?,
-            disconnected_callback: get_callback(*cx, prototype, b"disconnectedCallback\0")?,
-            adopted_callback: get_callback(*cx, prototype, b"adoptedCallback\0")?,
-            attribute_changed_callback: get_callback(
-                *cx,
-                prototype,
-                b"attributeChangedCallback\0",
-            )?,
+            connected_callback: get_callback(cx, prototype, b"connectedCallback\0")?,
+            disconnected_callback: get_callback(cx, prototype, b"disconnectedCallback\0")?,
+            adopted_callback: get_callback(cx, prototype, b"adoptedCallback\0")?,
+            attribute_changed_callback: get_callback(cx, prototype, b"attributeChangedCallback\0")?,
         })
     }
 
@@ -221,34 +217,32 @@ impl CustomElementRegistry {
 /// <https://html.spec.whatwg.org/multipage/#dom-customelementregistry-define>
 /// Step 10.4
 #[allow(unsafe_code)]
-unsafe fn get_callback(
-    cx: *mut JSContext,
+fn get_callback(
+    cx: JSContext,
     prototype: HandleObject,
     name: &[u8],
 ) -> Fallible<Option<Rc<Function>>> {
-    rooted!(in(cx) let mut callback = UndefinedValue());
-
-    // Step 10.4.1
-    if !JS_GetProperty(
-        cx,
-        prototype,
-        name.as_ptr() as *const _,
-        callback.handle_mut(),
-    ) {
-        return Err(Error::JSFailed);
-    }
-
-    // Step 10.4.2
-    if !callback.is_undefined() {
-        if !callback.is_object() || !IsCallable(callback.to_object()) {
-            return Err(Error::Type("Lifecycle callback is not callable".to_owned()));
+    rooted!(in(*cx) let mut callback = UndefinedValue());
+    unsafe {
+        // Step 10.4.1
+        if !JS_GetProperty(
+            *cx,
+            prototype,
+            name.as_ptr() as *const _,
+            callback.handle_mut(),
+        ) {
+            return Err(Error::JSFailed);
+        }
+
+        // Step 10.4.2
+        if !callback.is_undefined() {
+            if !callback.is_object() || !IsCallable(callback.to_object()) {
+                return Err(Error::Type("Lifecycle callback is not callable".to_owned()));
+            }
+            Ok(Some(Function::new(cx, callback.to_object())))
+        } else {
+            Ok(None)
         }
-        Ok(Some(Function::new(
-            SafeJSContext::from_ptr(cx),
-            callback.to_object(),
-        )))
-    } else {
-        Ok(None)
     }
 }
 
@@ -409,7 +403,7 @@ impl CustomElementRegistryMethods for CustomElementRegistry {
 
     /// <https://html.spec.whatwg.org/multipage/#dom-customelementregistry-get>
     #[allow(unsafe_code)]
-    fn Get(&self, cx: SafeJSContext, name: DOMString) -> JSVal {
+    fn Get(&self, cx: JSContext, name: DOMString) -> JSVal {
         match self.definitions.borrow().get(&LocalName::from(&*name)) {
             Some(definition) => unsafe {
                 rooted!(in(*cx) let mut constructor = UndefinedValue());
@@ -631,7 +625,7 @@ pub fn upgrade_element(definition: Rc<CustomElementDefinition>, element: &Elemen
         let global = GlobalScope::current().expect("No current global");
         let cx = global.get_cx();
         unsafe {
-            throw_dom_exception(*cx, &global, error);
+            throw_dom_exception(cx, &global, error);
             report_pending_exception(*cx, true);
         }
         return;
diff --git a/components/script/dom/filereader.rs b/components/script/dom/filereader.rs
index fdba0e0aa75..1a1a734d5b0 100644
--- a/components/script/dom/filereader.rs
+++ b/components/script/dom/filereader.rs
@@ -22,7 +22,7 @@ use crate::dom::event::{Event, EventBubbles, EventCancelable};
 use crate::dom::eventtarget::EventTarget;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::progressevent::ProgressEvent;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use crate::task::TaskCanceller;
 use crate::task_source::file_reading::{FileReadingTask, FileReadingTaskSource};
 use crate::task_source::{TaskSource, TaskSourceName};
@@ -30,7 +30,6 @@ use base64;
 use dom_struct::dom_struct;
 use encoding_rs::{Encoding, UTF_8};
 use js::jsapi::Heap;
-use js::jsapi::JSContext;
 use js::jsapi::JSObject;
 use js::jsval::{self, JSVal};
 use js::typedarray::{ArrayBuffer, CreateWith};
@@ -233,7 +232,6 @@ impl FileReader {
     }
 
     // https://w3c.github.io/FileAPI/#dfn-readAsText
-    #[allow(unsafe_code)]
     pub fn process_read_eof(
         filereader: TrustedFileReader,
         gen_id: GenerationId,
@@ -266,7 +264,7 @@ impl FileReader {
                 let _ac = enter_realm(&*fr);
                 FileReader::perform_readasarraybuffer(
                     &fr.result,
-                    *fr.global().get_cx(),
+                    fr.global().get_cx(),
                     data,
                     &blob_contents,
                 )
@@ -313,14 +311,14 @@ impl FileReader {
     #[allow(unsafe_code)]
     fn perform_readasarraybuffer(
         result: &DomRefCell<Option<FileReaderResult>>,
-        cx: *mut JSContext,
+        cx: JSContext,
         _: ReadMetaData,
         bytes: &[u8],
     ) {
         unsafe {
-            rooted!(in(cx) let mut array_buffer = ptr::null_mut::<JSObject>());
+            rooted!(in(*cx) let mut array_buffer = ptr::null_mut::<JSObject>());
             assert!(
-                ArrayBuffer::create(cx, CreateWith::Slice(bytes), array_buffer.handle_mut())
+                ArrayBuffer::create(*cx, CreateWith::Slice(bytes), array_buffer.handle_mut())
                     .is_ok()
             );
 
@@ -392,7 +390,7 @@ impl FileReaderMethods for FileReader {
 
     #[allow(unsafe_code)]
     // https://w3c.github.io/FileAPI/#dfn-result
-    fn GetResult(&self, _: SafeJSContext) -> Option<StringOrObject> {
+    fn GetResult(&self, _: JSContext) -> Option<StringOrObject> {
         self.result.borrow().as_ref().map(|r| match *r {
             FileReaderResult::String(ref string) => StringOrObject::String(string.clone()),
             FileReaderResult::ArrayBuffer(ref arr_buffer) => {
diff --git a/components/script/dom/globalscope.rs b/components/script/dom/globalscope.rs
index ddf7dfc61cc..2ae306e25be 100644
--- a/components/script/dom/globalscope.rs
+++ b/components/script/dom/globalscope.rs
@@ -677,23 +677,17 @@ impl GlobalScope {
     }
 
     /// Perform a microtask checkpoint.
-    #[allow(unsafe_code)]
     pub fn perform_a_microtask_checkpoint(&self) {
-        unsafe {
-            self.microtask_queue.checkpoint(
-                *self.get_cx(),
-                |_| Some(DomRoot::from_ref(self)),
-                vec![DomRoot::from_ref(self)],
-            );
-        }
+        self.microtask_queue.checkpoint(
+            self.get_cx(),
+            |_| Some(DomRoot::from_ref(self)),
+            vec![DomRoot::from_ref(self)],
+        );
     }
 
     /// Enqueue a microtask for subsequent execution.
-    #[allow(unsafe_code)]
     pub fn enqueue_microtask(&self, job: Microtask) {
-        unsafe {
-            self.microtask_queue.enqueue(job, *self.get_cx());
-        }
+        self.microtask_queue.enqueue(job, self.get_cx());
     }
 
     /// Create a new sender/receiver pair that can be used to implement an on-demand
diff --git a/components/script/dom/history.rs b/components/script/dom/history.rs
index 583c58a00f1..92c27dfb82d 100644
--- a/components/script/dom/history.rs
+++ b/components/script/dom/history.rs
@@ -18,9 +18,9 @@ use crate::dom::globalscope::GlobalScope;
 use crate::dom::hashchangeevent::HashChangeEvent;
 use crate::dom::popstateevent::PopStateEvent;
 use crate::dom::window::Window;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use dom_struct::dom_struct;
-use js::jsapi::{Heap, JSContext};
+use js::jsapi::Heap;
 use js::jsval::{JSVal, NullValue, UndefinedValue};
 use js::rust::HandleValue;
 use msg::constellation_msg::{HistoryStateId, TraversalDirection};
@@ -165,7 +165,7 @@ impl History {
     // https://html.spec.whatwg.org/multipage/#dom-history-replacestate
     fn push_or_replace_state(
         &self,
-        cx: *mut JSContext,
+        cx: JSContext,
         data: HandleValue,
         _title: DOMString,
         url: Option<USVString>,
@@ -185,7 +185,7 @@ impl History {
         // TODO: Step 4
 
         // Step 5
-        let serialized_data = StructuredCloneData::write(cx, data)?.move_to_arraybuffer();
+        let serialized_data = StructuredCloneData::write(*cx, data)?.move_to_arraybuffer();
 
         let new_url: ServoUrl = match url {
             // Step 6
@@ -265,7 +265,7 @@ impl History {
 
         // Step 11
         let global_scope = self.window.upcast::<GlobalScope>();
-        rooted!(in(cx) let mut state = UndefinedValue());
+        rooted!(in(*cx) let mut state = UndefinedValue());
         StructuredCloneData::Vector(serialized_data).read(&global_scope, state.handle_mut());
 
         // Step 12
@@ -280,7 +280,7 @@ impl History {
 
 impl HistoryMethods for History {
     // https://html.spec.whatwg.org/multipage/#dom-history-state
-    fn GetState(&self, _cx: SafeJSContext) -> Fallible<JSVal> {
+    fn GetState(&self, _cx: JSContext) -> Fallible<JSVal> {
         if !self.window.Document().is_fully_active() {
             return Err(Error::Security);
         }
@@ -329,22 +329,22 @@ impl HistoryMethods for History {
     // https://html.spec.whatwg.org/multipage/#dom-history-pushstate
     fn PushState(
         &self,
-        cx: SafeJSContext,
+        cx: JSContext,
         data: HandleValue,
         title: DOMString,
         url: Option<USVString>,
     ) -> ErrorResult {
-        self.push_or_replace_state(*cx, data, title, url, PushOrReplace::Push)
+        self.push_or_replace_state(cx, data, title, url, PushOrReplace::Push)
     }
 
     // https://html.spec.whatwg.org/multipage/#dom-history-replacestate
     fn ReplaceState(
         &self,
-        cx: SafeJSContext,
+        cx: JSContext,
         data: HandleValue,
         title: DOMString,
         url: Option<USVString>,
     ) -> ErrorResult {
-        self.push_or_replace_state(*cx, data, title, url, PushOrReplace::Replace)
+        self.push_or_replace_state(cx, data, title, url, PushOrReplace::Replace)
     }
 }
diff --git a/components/script/dom/htmlcanvaselement.rs b/components/script/dom/htmlcanvaselement.rs
index 4e9abe5f3c9..1c07a88cc1c 100644
--- a/components/script/dom/htmlcanvaselement.rs
+++ b/components/script/dom/htmlcanvaselement.rs
@@ -28,7 +28,7 @@ use crate::dom::webgl2renderingcontext::WebGL2RenderingContext;
 use crate::dom::webglrenderingcontext::{
     LayoutCanvasWebGLRenderingContextHelpers, WebGLRenderingContext,
 };
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use base64;
 use canvas_traits::canvas::{CanvasId, CanvasMsg, FromScriptMsg};
 use canvas_traits::webgl::{GLContextAttributes, WebGLVersion};
@@ -39,7 +39,6 @@ use image::png::PNGEncoder;
 use image::ColorType;
 use ipc_channel::ipc::IpcSharedMemory;
 use js::error::throw_type_error;
-use js::jsapi::JSContext;
 use js::rust::HandleValue;
 use profile_traits::ipc;
 use script_layout_interface::{HTMLCanvasData, HTMLCanvasDataSource};
@@ -207,10 +206,9 @@ impl HTMLCanvasElement {
         Some(context)
     }
 
-    #[allow(unsafe_code)]
-    unsafe fn get_or_init_webgl_context(
+    fn get_or_init_webgl_context(
         &self,
-        cx: *mut JSContext,
+        cx: JSContext,
         options: HandleValue,
     ) -> Option<DomRoot<WebGLRenderingContext>> {
         if let Some(ctx) = self.context() {
@@ -227,10 +225,9 @@ impl HTMLCanvasElement {
         Some(context)
     }
 
-    #[allow(unsafe_code)]
-    unsafe fn get_or_init_webgl2_context(
+    fn get_or_init_webgl2_context(
         &self,
-        cx: *mut JSContext,
+        cx: JSContext,
         options: HandleValue,
     ) -> Option<DomRoot<WebGL2RenderingContext>> {
         if !pref!(dom.webgl2.enabled) {
@@ -260,20 +257,19 @@ impl HTMLCanvasElement {
     }
 
     #[allow(unsafe_code)]
-    unsafe fn get_gl_attributes(
-        cx: *mut JSContext,
-        options: HandleValue,
-    ) -> Option<GLContextAttributes> {
-        match WebGLContextAttributes::new(SafeJSContext::from_ptr(cx), options) {
-            Ok(ConversionResult::Success(ref attrs)) => Some(From::from(attrs)),
-            Ok(ConversionResult::Failure(ref error)) => {
-                throw_type_error(cx, &error);
-                None
-            },
-            _ => {
-                debug!("Unexpected error on conversion of WebGLContextAttributes");
-                None
-            },
+    fn get_gl_attributes(cx: JSContext, options: HandleValue) -> Option<GLContextAttributes> {
+        unsafe {
+            match WebGLContextAttributes::new(cx, options) {
+                Ok(ConversionResult::Success(ref attrs)) => Some(From::from(attrs)),
+                Ok(ConversionResult::Failure(ref error)) => {
+                    throw_type_error(*cx, &error);
+                    None
+                },
+                _ => {
+                    debug!("Unexpected error on conversion of WebGLContextAttributes");
+                    None
+                },
+            }
         }
     }
 
@@ -329,10 +325,9 @@ impl HTMLCanvasElementMethods for HTMLCanvasElement {
     make_uint_setter!(SetHeight, "height", DEFAULT_HEIGHT);
 
     // https://html.spec.whatwg.org/multipage/#dom-canvas-getcontext
-    #[allow(unsafe_code)]
     fn GetContext(
         &self,
-        cx: SafeJSContext,
+        cx: JSContext,
         id: DOMString,
         options: HandleValue,
     ) -> Option<RenderingContext> {
@@ -340,14 +335,12 @@ impl HTMLCanvasElementMethods for HTMLCanvasElement {
             "2d" => self
                 .get_or_init_2d_context()
                 .map(RenderingContext::CanvasRenderingContext2D),
-            "webgl" | "experimental-webgl" => unsafe {
-                self.get_or_init_webgl_context(*cx, options)
-                    .map(RenderingContext::WebGLRenderingContext)
-            },
-            "webgl2" | "experimental-webgl2" => unsafe {
-                self.get_or_init_webgl2_context(*cx, options)
-                    .map(RenderingContext::WebGL2RenderingContext)
-            },
+            "webgl" | "experimental-webgl" => self
+                .get_or_init_webgl_context(cx, options)
+                .map(RenderingContext::WebGLRenderingContext),
+            "webgl2" | "experimental-webgl2" => self
+                .get_or_init_webgl2_context(cx, options)
+                .map(RenderingContext::WebGL2RenderingContext),
             _ => None,
         }
     }
@@ -355,7 +348,7 @@ impl HTMLCanvasElementMethods for HTMLCanvasElement {
     // https://html.spec.whatwg.org/multipage/#dom-canvas-todataurl
     fn ToDataURL(
         &self,
-        _context: SafeJSContext,
+        _context: JSContext,
         _mime_type: Option<DOMString>,
         _quality: HandleValue,
     ) -> Fallible<USVString> {
diff --git a/components/script/dom/permissions.rs b/components/script/dom/permissions.rs
index 419115d1240..fba7965eee1 100644
--- a/components/script/dom/permissions.rs
+++ b/components/script/dom/permissions.rs
@@ -17,10 +17,10 @@ use crate::dom::bluetoothpermissionresult::BluetoothPermissionResult;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::permissionstatus::PermissionStatus;
 use crate::dom::promise::Promise;
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use dom_struct::dom_struct;
 use js::conversions::ConversionResult;
-use js::jsapi::{JSContext, JSObject};
+use js::jsapi::JSObject;
 use js::jsval::{ObjectValue, UndefinedValue};
 use servo_config::pref;
 use std::rc::Rc;
@@ -37,17 +37,17 @@ pub trait PermissionAlgorithm {
     type Descriptor;
     type Status;
     fn create_descriptor(
-        cx: *mut JSContext,
+        cx: JSContext,
         permission_descriptor_obj: *mut JSObject,
     ) -> Result<Self::Descriptor, Error>;
     fn permission_query(
-        cx: *mut JSContext,
+        cx: JSContext,
         promise: &Rc<Promise>,
         descriptor: &Self::Descriptor,
         status: &Self::Status,
     );
     fn permission_request(
-        cx: *mut JSContext,
+        cx: JSContext,
         promise: &Rc<Promise>,
         descriptor: &Self::Descriptor,
         status: &Self::Status,
@@ -88,7 +88,7 @@ impl Permissions {
     fn manipulate(
         &self,
         op: Operation,
-        cx: *mut JSContext,
+        cx: JSContext,
         permissionDesc: *mut JSObject,
         promise: Option<Rc<Promise>>,
     ) -> Rc<Promise> {
@@ -201,18 +201,18 @@ impl Permissions {
 
 impl PermissionsMethods for Permissions {
     // https://w3c.github.io/permissions/#dom-permissions-query
-    fn Query(&self, cx: SafeJSContext, permissionDesc: *mut JSObject) -> Rc<Promise> {
-        self.manipulate(Operation::Query, *cx, permissionDesc, None)
+    fn Query(&self, cx: JSContext, permissionDesc: *mut JSObject) -> Rc<Promise> {
+        self.manipulate(Operation::Query, cx, permissionDesc, None)
     }
 
     // https://w3c.github.io/permissions/#dom-permissions-request
-    fn Request(&self, cx: SafeJSContext, permissionDesc: *mut JSObject) -> Rc<Promise> {
-        self.manipulate(Operation::Request, *cx, permissionDesc, None)
+    fn Request(&self, cx: JSContext, permissionDesc: *mut JSObject) -> Rc<Promise> {
+        self.manipulate(Operation::Request, cx, permissionDesc, None)
     }
 
     // https://w3c.github.io/permissions/#dom-permissions-revoke
-    fn Revoke(&self, cx: SafeJSContext, permissionDesc: *mut JSObject) -> Rc<Promise> {
-        self.manipulate(Operation::Revoke, *cx, permissionDesc, None)
+    fn Revoke(&self, cx: JSContext, permissionDesc: *mut JSObject) -> Rc<Promise> {
+        self.manipulate(Operation::Revoke, cx, permissionDesc, None)
     }
 }
 
@@ -220,27 +220,24 @@ impl PermissionAlgorithm for Permissions {
     type Descriptor = PermissionDescriptor;
     type Status = PermissionStatus;
 
-    #[allow(unsafe_code)]
     fn create_descriptor(
-        cx: *mut JSContext,
+        cx: JSContext,
         permission_descriptor_obj: *mut JSObject,
     ) -> Result<PermissionDescriptor, Error> {
-        rooted!(in(cx) let mut property = UndefinedValue());
+        rooted!(in(*cx) let mut property = UndefinedValue());
         property
             .handle_mut()
             .set(ObjectValue(permission_descriptor_obj));
-        unsafe {
-            match PermissionDescriptor::new(SafeJSContext::from_ptr(cx), property.handle()) {
-                Ok(ConversionResult::Success(descriptor)) => Ok(descriptor),
-                Ok(ConversionResult::Failure(error)) => Err(Error::Type(error.into_owned())),
-                Err(_) => Err(Error::JSFailed),
-            }
+        match PermissionDescriptor::new(cx, property.handle()) {
+            Ok(ConversionResult::Success(descriptor)) => Ok(descriptor),
+            Ok(ConversionResult::Failure(error)) => Err(Error::Type(error.into_owned())),
+            Err(_) => Err(Error::JSFailed),
         }
     }
 
     // https://w3c.github.io/permissions/#boolean-permission-query-algorithm
     fn permission_query(
-        _cx: *mut JSContext,
+        _cx: JSContext,
         _promise: &Rc<Promise>,
         _descriptor: &PermissionDescriptor,
         status: &PermissionStatus,
@@ -251,7 +248,7 @@ impl PermissionAlgorithm for Permissions {
 
     // https://w3c.github.io/permissions/#boolean-permission-request-algorithm
     fn permission_request(
-        cx: *mut JSContext,
+        cx: JSContext,
         promise: &Rc<Promise>,
         descriptor: &PermissionDescriptor,
         status: &PermissionStatus,
diff --git a/components/script/dom/promise.rs b/components/script/dom/promise.rs
index 4dd6f53e711..b101c449348 100644
--- a/components/script/dom/promise.rs
+++ b/components/script/dom/promise.rs
@@ -18,6 +18,7 @@ use crate::dom::bindings::reflector::{DomObject, MutDomObject, Reflector};
 use crate::dom::bindings::utils::AsCCharPtrPtr;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::promisenativehandler::PromiseNativeHandler;
+use crate::script_runtime::JSContext as SafeJSContext;
 use dom_struct::dom_struct;
 use js::conversions::ToJSValConvertible;
 use js::jsapi::{AddRawValueRoot, CallArgs, GetFunctionNativeReserved};
@@ -49,20 +50,21 @@ pub struct Promise {
 
 /// Private helper to enable adding new methods to Rc<Promise>.
 trait PromiseHelper {
-    #[allow(unsafe_code)]
-    unsafe fn initialize(&self, cx: *mut JSContext);
+    fn initialize(&self, cx: SafeJSContext);
 }
 
 impl PromiseHelper for Rc<Promise> {
     #[allow(unsafe_code)]
-    unsafe fn initialize(&self, cx: *mut JSContext) {
+    fn initialize(&self, cx: SafeJSContext) {
         let obj = self.reflector().get_jsobject();
         self.permanent_js_root.set(ObjectValue(*obj));
-        assert!(AddRawValueRoot(
-            cx,
-            self.permanent_js_root.get_unsafe(),
-            b"Promise::root\0".as_c_char_ptr()
-        ));
+        unsafe {
+            assert!(AddRawValueRoot(
+                *cx,
+                self.permanent_js_root.get_unsafe(),
+                b"Promise::root\0".as_c_char_ptr()
+            ));
+        }
     }
 }
 
@@ -86,75 +88,72 @@ impl Promise {
         Promise::new_in_current_compartment(global, comp)
     }
 
-    #[allow(unsafe_code)]
     pub fn new_in_current_compartment(global: &GlobalScope, _comp: InCompartment) -> Rc<Promise> {
         let cx = global.get_cx();
         rooted!(in(*cx) let mut obj = ptr::null_mut::<JSObject>());
-        unsafe {
-            Promise::create_js_promise(*cx, HandleObject::null(), obj.handle_mut());
-            Promise::new_with_js_promise(obj.handle(), *cx)
-        }
+        Promise::create_js_promise(cx, HandleObject::null(), obj.handle_mut());
+        Promise::new_with_js_promise(obj.handle(), cx)
     }
 
     #[allow(unsafe_code)]
     pub fn duplicate(&self) -> Rc<Promise> {
         let cx = self.global().get_cx();
-        unsafe { Promise::new_with_js_promise(self.reflector().get_jsobject(), *cx) }
+        Promise::new_with_js_promise(self.reflector().get_jsobject(), cx)
     }
 
     #[allow(unsafe_code, unrooted_must_root)]
-    pub unsafe fn new_with_js_promise(obj: HandleObject, cx: *mut JSContext) -> Rc<Promise> {
-        assert!(IsPromiseObject(obj));
-        let promise = Promise {
-            reflector: Reflector::new(),
-            permanent_js_root: Heap::default(),
-        };
-        let mut promise = Rc::new(promise);
-        Rc::get_mut(&mut promise).unwrap().init_reflector(obj.get());
-        promise.initialize(cx);
-        promise
+    pub fn new_with_js_promise(obj: HandleObject, cx: SafeJSContext) -> Rc<Promise> {
+        unsafe {
+            assert!(IsPromiseObject(obj));
+            let promise = Promise {
+                reflector: Reflector::new(),
+                permanent_js_root: Heap::default(),
+            };
+            let mut promise = Rc::new(promise);
+            Rc::get_mut(&mut promise).unwrap().init_reflector(obj.get());
+            promise.initialize(cx);
+            promise
+        }
     }
 
     #[allow(unsafe_code)]
-    unsafe fn create_js_promise(
-        cx: *mut JSContext,
-        proto: HandleObject,
-        mut obj: MutableHandleObject,
-    ) {
-        let do_nothing_func = JS_NewFunction(
-            cx,
-            Some(do_nothing_promise_executor),
-            /* nargs = */ 2,
-            /* flags = */ 0,
-            ptr::null(),
-        );
-        assert!(!do_nothing_func.is_null());
-        rooted!(in(cx) let do_nothing_obj = JS_GetFunctionObject(do_nothing_func));
-        assert!(!do_nothing_obj.is_null());
-        obj.set(NewPromiseObject(cx, do_nothing_obj.handle(), proto));
-        assert!(!obj.is_null());
+    fn create_js_promise(cx: SafeJSContext, proto: HandleObject, mut obj: MutableHandleObject) {
+        unsafe {
+            let do_nothing_func = JS_NewFunction(
+                *cx,
+                Some(do_nothing_promise_executor),
+                /* nargs = */ 2,
+                /* flags = */ 0,
+                ptr::null(),
+            );
+            assert!(!do_nothing_func.is_null());
+            rooted!(in(*cx) let do_nothing_obj = JS_GetFunctionObject(do_nothing_func));
+            assert!(!do_nothing_obj.is_null());
+            obj.set(NewPromiseObject(*cx, do_nothing_obj.handle(), proto));
+            assert!(!obj.is_null());
+        }
     }
 
     #[allow(unrooted_must_root, unsafe_code)]
-    pub unsafe fn new_resolved(
+    pub fn new_resolved(
         global: &GlobalScope,
-        cx: *mut JSContext,
+        cx: SafeJSContext,
         value: HandleValue,
     ) -> Fallible<Rc<Promise>> {
-        let _ac = JSAutoRealm::new(cx, global.reflector().get_jsobject().get());
-        rooted!(in(cx) let p = CallOriginalPromiseResolve(cx, value));
+        let _ac = JSAutoRealm::new(*cx, global.reflector().get_jsobject().get());
+        rooted!(in(*cx) let p = unsafe { CallOriginalPromiseResolve(*cx, value) });
         assert!(!p.handle().is_null());
         Ok(Promise::new_with_js_promise(p.handle(), cx))
     }
 
     #[allow(unrooted_must_root, unsafe_code)]
-    pub unsafe fn new_rejected(
+    pub fn new_rejected(
         global: &GlobalScope,
-        cx: *mut JSContext,
+        cx: SafeJSContext,
         value: HandleValue,
     ) -> Fallible<Rc<Promise>> {
-        let _ac = JSAutoRealm::new(cx, global.reflector().get_jsobject().get());
-        rooted!(in(cx) let p = CallOriginalPromiseReject(cx, value));
+        let _ac = JSAutoRealm::new(*cx, global.reflector().get_jsobject().get());
+        rooted!(in(*cx) let p = unsafe { CallOriginalPromiseReject(*cx, value) });
         assert!(!p.handle().is_null());
         Ok(Promise::new_with_js_promise(p.handle(), cx))
     }
@@ -169,14 +168,16 @@ impl Promise {
         rooted!(in(*cx) let mut v = UndefinedValue());
         unsafe {
             val.to_jsval(*cx, v.handle_mut());
-            self.resolve(*cx, v.handle());
         }
+        self.resolve(cx, v.handle());
     }
 
     #[allow(unrooted_must_root, unsafe_code)]
-    pub unsafe fn resolve(&self, cx: *mut JSContext, value: HandleValue) {
-        if !ResolvePromise(cx, self.promise_obj(), value) {
-            JS_ClearPendingException(cx);
+    pub fn resolve(&self, cx: SafeJSContext, value: HandleValue) {
+        unsafe {
+            if !ResolvePromise(*cx, self.promise_obj(), value) {
+                JS_ClearPendingException(*cx);
+            }
         }
     }
 
@@ -190,8 +191,8 @@ impl Promise {
         rooted!(in(*cx) let mut v = UndefinedValue());
         unsafe {
             val.to_jsval(*cx, v.handle_mut());
-            self.reject(*cx, v.handle());
         }
+        self.reject(cx, v.handle());
     }
 
     #[allow(unsafe_code)]
@@ -201,14 +202,16 @@ impl Promise {
         rooted!(in(*cx) let mut v = UndefinedValue());
         unsafe {
             error.to_jsval(*cx, &self.global(), v.handle_mut());
-            self.reject(*cx, v.handle());
         }
+        self.reject(cx, v.handle());
     }
 
     #[allow(unrooted_must_root, unsafe_code)]
-    pub unsafe fn reject(&self, cx: *mut JSContext, value: HandleValue) {
-        if !RejectPromise(cx, self.promise_obj(), value) {
-            JS_ClearPendingException(cx);
+    pub fn reject(&self, cx: SafeJSContext, value: HandleValue) {
+        unsafe {
+            if !RejectPromise(*cx, self.promise_obj(), value) {
+                JS_ClearPendingException(*cx);
+            }
         }
     }
 
diff --git a/components/script/dom/testbinding.rs b/components/script/dom/testbinding.rs
index dfa148e5c11..607c97085f1 100644
--- a/components/script/dom/testbinding.rs
+++ b/components/script/dom/testbinding.rs
@@ -941,29 +941,21 @@ impl TestBindingMethods for TestBinding {
     }
 
     #[allow(unrooted_must_root)]
-    #[allow(unsafe_code)]
     fn ReturnResolvedPromise(&self, cx: SafeJSContext, v: HandleValue) -> Fallible<Rc<Promise>> {
-        unsafe { Promise::new_resolved(&self.global(), *cx, v) }
+        Promise::new_resolved(&self.global(), cx, v)
     }
 
     #[allow(unrooted_must_root)]
-    #[allow(unsafe_code)]
     fn ReturnRejectedPromise(&self, cx: SafeJSContext, v: HandleValue) -> Fallible<Rc<Promise>> {
-        unsafe { Promise::new_rejected(&self.global(), *cx, v) }
+        Promise::new_rejected(&self.global(), cx, v)
     }
 
-    #[allow(unsafe_code)]
     fn PromiseResolveNative(&self, cx: SafeJSContext, p: &Promise, v: HandleValue) {
-        unsafe {
-            p.resolve(*cx, v);
-        }
+        p.resolve(cx, v);
     }
 
-    #[allow(unsafe_code)]
     fn PromiseRejectNative(&self, cx: SafeJSContext, p: &Promise, v: HandleValue) {
-        unsafe {
-            p.reject(*cx, v);
-        }
+        p.reject(cx, v);
     }
 
     fn PromiseRejectWithTypeError(&self, p: &Promise, s: USVString) {
@@ -1098,12 +1090,11 @@ impl TestBinding {
     pub fn FuncControlledStaticMethodEnabled(_: &GlobalScope) {}
 }
 
-#[allow(unsafe_code)]
 impl TestBinding {
-    pub unsafe fn condition_satisfied(_: *mut JSContext, _: HandleObject) -> bool {
+    pub fn condition_satisfied(_: SafeJSContext, _: HandleObject) -> bool {
         true
     }
-    pub unsafe fn condition_unsatisfied(_: *mut JSContext, _: HandleObject) -> bool {
+    pub fn condition_unsatisfied(_: SafeJSContext, _: HandleObject) -> bool {
         false
     }
 }
diff --git a/components/script/dom/windowproxy.rs b/components/script/dom/windowproxy.rs
index dbdd09eabb9..99336ec7f66 100644
--- a/components/script/dom/windowproxy.rs
+++ b/components/script/dom/windowproxy.rs
@@ -18,6 +18,7 @@ use crate::dom::document::Document;
 use crate::dom::element::Element;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::window::Window;
+use crate::script_runtime::JSContext as SafeJSContext;
 use crate::script_thread::ScriptThread;
 use dom_struct::dom_struct;
 use embedder_traits::EmbedderMsg;
@@ -959,7 +960,7 @@ pub fn new_window_proxy_handler() -> WindowProxyHandler {
 unsafe fn throw_security_error(cx: *mut JSContext) -> bool {
     if !JS_IsExceptionPending(cx) {
         let global = GlobalScope::from_context(cx);
-        throw_dom_exception(cx, &*global, Error::Security);
+        throw_dom_exception(SafeJSContext::from_ptr(cx), &*global, Error::Security);
     }
     false
 }
diff --git a/components/script/dom/xmlhttprequest.rs b/components/script/dom/xmlhttprequest.rs
index 082973345c9..7f0dbdf68a2 100644
--- a/components/script/dom/xmlhttprequest.rs
+++ b/components/script/dom/xmlhttprequest.rs
@@ -38,7 +38,7 @@ use crate::dom::xmlhttprequesteventtarget::XMLHttpRequestEventTarget;
 use crate::dom::xmlhttprequestupload::XMLHttpRequestUpload;
 use crate::fetch::FetchCanceller;
 use crate::network_listener::{self, NetworkListener, PreInvoke, ResourceTimingListener};
-use crate::script_runtime::JSContext as SafeJSContext;
+use crate::script_runtime::JSContext;
 use crate::task_source::networking::NetworkingTaskSource;
 use crate::task_source::TaskSourceName;
 use crate::timers::{OneshotTimerCallback, OneshotTimerHandle};
@@ -54,7 +54,7 @@ use hyper_serde::Serde;
 use ipc_channel::ipc;
 use ipc_channel::router::ROUTER;
 use js::jsapi::JS_ClearPendingException;
-use js::jsapi::{Heap, JSContext, JSObject};
+use js::jsapi::{Heap, JSObject};
 use js::jsval::{JSVal, NullValue, UndefinedValue};
 use js::rust::wrappers::JS_ParseJSON;
 use js::typedarray::{ArrayBuffer, CreateWith};
@@ -878,7 +878,7 @@ impl XMLHttpRequestMethods for XMLHttpRequest {
 
     #[allow(unsafe_code)]
     // https://xhr.spec.whatwg.org/#the-response-attribute
-    fn Response(&self, cx: SafeJSContext) -> JSVal {
+    fn Response(&self, cx: JSContext) -> JSVal {
         rooted!(in(*cx) let mut rval = UndefinedValue());
         match self.response_type.get() {
             XMLHttpRequestResponseType::_empty | XMLHttpRequestResponseType::Text => unsafe {
@@ -902,16 +902,14 @@ impl XMLHttpRequestMethods for XMLHttpRequest {
                 self.document_response().to_jsval(*cx, rval.handle_mut());
             },
             XMLHttpRequestResponseType::Json => unsafe {
-                self.json_response(*cx).to_jsval(*cx, rval.handle_mut());
+                self.json_response(cx).to_jsval(*cx, rval.handle_mut());
             },
             XMLHttpRequestResponseType::Blob => unsafe {
                 self.blob_response().to_jsval(*cx, rval.handle_mut());
             },
-            XMLHttpRequestResponseType::Arraybuffer => unsafe {
-                match self.arraybuffer_response(*cx) {
-                    Some(js_object) => js_object.to_jsval(*cx, rval.handle_mut()),
-                    None => return NullValue(),
-                }
+            XMLHttpRequestResponseType::Arraybuffer => match self.arraybuffer_response(cx) {
+                Some(js_object) => unsafe { js_object.to_jsval(*cx, rval.handle_mut()) },
+                None => return NullValue(),
             },
         }
         rval.get()
@@ -1278,7 +1276,7 @@ impl XMLHttpRequest {
 
     // https://xhr.spec.whatwg.org/#arraybuffer-response
     #[allow(unsafe_code)]
-    unsafe fn arraybuffer_response(&self, cx: *mut JSContext) -> Option<NonNull<JSObject>> {
+    fn arraybuffer_response(&self, cx: JSContext) -> Option<NonNull<JSObject>> {
         // Step 1
         let created = self.response_arraybuffer.get();
         if let Some(nonnull) = NonNull::new(created) {
@@ -1287,13 +1285,15 @@ impl XMLHttpRequest {
 
         // Step 2
         let bytes = self.response.borrow();
-        rooted!(in(cx) let mut array_buffer = ptr::null_mut::<JSObject>());
-        ArrayBuffer::create(cx, CreateWith::Slice(&bytes), array_buffer.handle_mut())
-            .ok()
-            .and_then(|()| {
-                self.response_arraybuffer.set(array_buffer.get());
-                Some(NonNull::new_unchecked(array_buffer.get()))
-            })
+        rooted!(in(*cx) let mut array_buffer = ptr::null_mut::<JSObject>());
+        unsafe {
+            ArrayBuffer::create(*cx, CreateWith::Slice(&bytes), array_buffer.handle_mut())
+                .ok()
+                .and_then(|()| {
+                    self.response_arraybuffer.set(array_buffer.get());
+                    Some(NonNull::new_unchecked(array_buffer.get()))
+                })
+        }
     }
 
     // https://xhr.spec.whatwg.org/#document-response
@@ -1345,7 +1345,7 @@ impl XMLHttpRequest {
 
     #[allow(unsafe_code)]
     // https://xhr.spec.whatwg.org/#json-response
-    fn json_response(&self, cx: *mut JSContext) -> JSVal {
+    fn json_response(&self, cx: JSContext) -> JSVal {
         // Step 1
         let response_json = self.response_json.get();
         if !response_json.is_null_or_undefined() {
@@ -1378,15 +1378,15 @@ impl XMLHttpRequest {
         // if present, but UTF-16BE/LE BOM must not be honored.
         let json_text = decode_to_utf16_with_bom_removal(&bytes, UTF_8);
         // Step 5
-        rooted!(in(cx) let mut rval = UndefinedValue());
+        rooted!(in(*cx) let mut rval = UndefinedValue());
         unsafe {
             if !JS_ParseJSON(
-                cx,
+                *cx,
                 json_text.as_ptr(),
                 json_text.len() as u32,
                 rval.handle_mut(),
             ) {
-                JS_ClearPendingException(cx);
+                JS_ClearPendingException(*cx);
                 return NullValue();
             }
         }
diff --git a/components/script/microtask.rs b/components/script/microtask.rs
index db420e20eaa..001262c05e1 100644
--- a/components/script/microtask.rs
+++ b/components/script/microtask.rs
@@ -14,9 +14,9 @@ use crate::dom::globalscope::GlobalScope;
 use crate::dom::htmlimageelement::ImageElementMicrotask;
 use crate::dom::htmlmediaelement::MediaElementMicrotask;
 use crate::dom::mutationobserver::MutationObserver;
-use crate::script_runtime::notify_about_rejected_promises;
+use crate::script_runtime::{notify_about_rejected_promises, JSContext};
 use crate::script_thread::ScriptThread;
-use js::jsapi::{JSContext, JobQueueIsEmpty, JobQueueMayNotBeEmpty};
+use js::jsapi::{JobQueueIsEmpty, JobQueueMayNotBeEmpty};
 use msg::constellation_msg::PipelineId;
 use std::cell::Cell;
 use std::mem;
@@ -56,17 +56,17 @@ impl MicrotaskQueue {
     /// Add a new microtask to this queue. It will be invoked as part of the next
     /// microtask checkpoint.
     #[allow(unsafe_code)]
-    pub unsafe fn enqueue(&self, job: Microtask, cx: *mut JSContext) {
+    pub fn enqueue(&self, job: Microtask, cx: JSContext) {
         self.microtask_queue.borrow_mut().push(job);
-        JobQueueMayNotBeEmpty(cx);
+        unsafe { JobQueueMayNotBeEmpty(*cx) };
     }
 
     /// <https://html.spec.whatwg.org/multipage/#perform-a-microtask-checkpoint>
     /// Perform a microtask checkpoint, executing all queued microtasks until the queue is empty.
     #[allow(unsafe_code)]
-    pub unsafe fn checkpoint<F>(
+    pub fn checkpoint<F>(
         &self,
-        cx: *mut JSContext,
+        cx: JSContext,
         target_provider: F,
         globalscopes: Vec<DomRoot<GlobalScope>>,
     ) where
@@ -86,7 +86,7 @@ impl MicrotaskQueue {
 
             for (idx, job) in pending_queue.iter().enumerate() {
                 if idx == pending_queue.len() - 1 && self.microtask_queue.borrow().is_empty() {
-                    JobQueueIsEmpty(cx);
+                    unsafe { JobQueueIsEmpty(*cx) };
                 }
 
                 match *job {
diff --git a/components/script/script_runtime.rs b/components/script/script_runtime.rs
index fb94d30fafd..a460d1af1b5 100644
--- a/components/script/script_runtime.rs
+++ b/components/script/script_runtime.rs
@@ -172,6 +172,7 @@ unsafe extern "C" fn enqueue_promise_job(
     _allocation_site: HandleObject,
     incumbent_global: HandleObject,
 ) -> bool {
+    let cx = JSContext::from_ptr(cx);
     wrap_panic(
         AssertUnwindSafe(|| {
             let microtask_queue = &*(extra as *const MicrotaskQueue);
@@ -179,7 +180,7 @@ unsafe extern "C" fn enqueue_promise_job(
             let pipeline = global.pipeline_id();
             microtask_queue.enqueue(
                 Microtask::Promise(EnqueuedPromiseCallback {
-                    callback: PromiseJobCallback::new(JSContext::from_ptr(cx), job.get()),
+                    callback: PromiseJobCallback::new(cx, job.get()),
                     pipeline,
                 }),
                 cx,
@@ -201,7 +202,8 @@ unsafe extern "C" fn promise_rejection_tracker(
     // TODO: Step 2 - If script's muted errors is true, terminate these steps.
 
     // Step 3.
-    let global = GlobalScope::from_context(cx);
+    let cx = JSContext::from_ptr(cx);
+    let global = GlobalScope::from_context(*cx);
 
     wrap_panic(
         AssertUnwindSafe(|| {
@@ -281,7 +283,7 @@ pub fn notify_about_rejected_promises(global: &GlobalScope) {
                 .iter()
                 .map(|promise| {
                     let promise =
-                        Promise::new_with_js_promise(Handle::from_raw(promise.handle()), *cx);
+                        Promise::new_with_js_promise(Handle::from_raw(promise.handle()), cx);
 
                     TrustedPromise::new(promise)
                 })
diff --git a/components/script/script_thread.rs b/components/script/script_thread.rs
index da5d8f2e7aa..06442d3042a 100644
--- a/components/script/script_thread.rs
+++ b/components/script/script_thread.rs
@@ -910,16 +910,13 @@ impl ScriptThread {
     }
 
     // https://html.spec.whatwg.org/multipage/#await-a-stable-state
-    #[allow(unsafe_code)]
     pub fn await_stable_state(task: Microtask) {
         SCRIPT_THREAD_ROOT.with(|root| {
             if let Some(script_thread) = root.get() {
-                unsafe {
-                    let script_thread = &*script_thread;
-                    script_thread
-                        .microtask_queue
-                        .enqueue(task, *script_thread.get_cx());
-                }
+                let script_thread = unsafe { &*script_thread };
+                script_thread
+                    .microtask_queue
+                    .enqueue(task, script_thread.get_cx());
             }
         });
     }
@@ -3776,17 +3773,15 @@ impl ScriptThread {
         }
     }
 
-    #[allow(unsafe_code)]
     pub fn enqueue_microtask(job: Microtask) {
-        SCRIPT_THREAD_ROOT.with(|root| unsafe {
-            let script_thread = &*root.get().unwrap();
+        SCRIPT_THREAD_ROOT.with(|root| {
+            let script_thread = unsafe { &*root.get().unwrap() };
             script_thread
                 .microtask_queue
-                .enqueue(job, *script_thread.get_cx());
+                .enqueue(job, script_thread.get_cx());
         });
     }
 
-    #[allow(unsafe_code)]
     fn perform_a_microtask_checkpoint(&self) {
         let globals = self
             .documents
@@ -3795,13 +3790,11 @@ impl ScriptThread {
             .map(|(_id, document)| document.global())
             .collect();
 
-        unsafe {
-            self.microtask_queue.checkpoint(
-                *self.get_cx(),
-                |id| self.documents.borrow().find_global(id),
-                globals,
-            )
-        }
+        self.microtask_queue.checkpoint(
+            self.get_cx(),
+            |id| self.documents.borrow().find_global(id),
+            globals,
+        )
     }
 }
 
diff --git a/components/script/webdriver_handlers.rs b/components/script/webdriver_handlers.rs
index c8aad9a6b4c..874f707a739 100644
--- a/components/script/webdriver_handlers.rs
+++ b/components/script/webdriver_handlers.rs
@@ -739,7 +739,7 @@ pub fn handle_get_property(
                         Err(_) => Ok(WebDriverJSValue::Undefined),
                     },
                     Err(error) => {
-                        unsafe { throw_dom_exception(*cx, &node.reflector().global(), error) };
+                        throw_dom_exception(cx, &node.reflector().global(), error);
                         Ok(WebDriverJSValue::Undefined)
                     },
                 }