diff --git a/components/script/dom/bindings/interface.rs b/components/script/dom/bindings/interface.rs
index 1085a137428..82303f800ba 100644
--- a/components/script/dom/bindings/interface.rs
+++ b/components/script/dom/bindings/interface.rs
@@ -16,6 +16,10 @@ use js::glue::UncheckedUnwrapObject;
 use js::jsapi::GetWellKnownSymbol;
 use js::jsapi::HandleObject as RawHandleObject;
 use js::jsapi::{jsid, JSClass, JSClassOps};
+use js::jsapi::{
+    Compartment, CompartmentSpecifier, IsSharableCompartment, IsSystemCompartment,
+    JS_IterateCompartments, JS::CompartmentIterResult,
+};
 use js::jsapi::{JSAutoRealm, JSContext, JSFunctionSpec, JSObject, JSFUN_CONSTRUCTOR};
 use js::jsapi::{JSPropertySpec, JSString, JSTracer, JS_AtomizeAndPinString};
 use js::jsapi::{JS_GetFunctionObject, JS_NewFunction, JS_NewGlobalObject};
@@ -139,6 +143,7 @@ pub unsafe fn create_global_object(
     options.creationOptions_.traceGlobal_ = Some(trace);
     options.creationOptions_.sharedMemoryAndAtomics_ = false;
     options.creationOptions_.streams_ = true;
+    select_compartment(cx, &mut options);
 
     rval.set(JS_NewGlobalObject(
         *cx,
@@ -162,6 +167,43 @@ pub unsafe fn create_global_object(
     JS_FireOnNewGlobalObject(*cx, rval.handle());
 }
 
+/// Choose the compartment to create a new global object in.
+fn select_compartment(cx: SafeJSContext, options: &mut RealmOptions) {
+    type Data = *mut Compartment;
+    unsafe extern "C" fn callback(
+        _cx: *mut JSContext,
+        data: *mut libc::c_void,
+        compartment: *mut Compartment,
+    ) -> CompartmentIterResult {
+        let data = data as *mut Data;
+
+        if !IsSharableCompartment(compartment) || IsSystemCompartment(compartment) {
+            return CompartmentIterResult::KeepGoing;
+        }
+
+        // Choose any sharable, non-system compartment in this context to allow
+        // same-agent documents to share JS and DOM objects.
+        *data = compartment;
+        CompartmentIterResult::Stop
+    }
+
+    let mut compartment: Data = ptr::null_mut();
+    unsafe {
+        JS_IterateCompartments(
+            *cx,
+            (&mut compartment) as *mut Data as *mut libc::c_void,
+            Some(callback),
+        );
+    }
+
+    if compartment.is_null() {
+        options.creationOptions_.compSpec_ = CompartmentSpecifier::NewCompartmentAndZone;
+    } else {
+        options.creationOptions_.compSpec_ = CompartmentSpecifier::ExistingCompartment;
+        options.creationOptions_.__bindgen_anon_1.comp_ = compartment;
+    }
+}
+
 /// Create and define the interface object of a callback interface.
 pub fn create_callback_interface_object(
     cx: SafeJSContext,
diff --git a/components/script/dom/windowproxy.rs b/components/script/dom/windowproxy.rs
index e37e561af06..0f92e4b3367 100644
--- a/components/script/dom/windowproxy.rs
+++ b/components/script/dom/windowproxy.rs
@@ -637,13 +637,11 @@ impl WindowProxy {
             // The old window proxy no longer owns this browsing context.
             SetProxyReservedSlot(old_js_proxy.get(), 0, &PrivateValue(ptr::null_mut()));
 
-            // Brain transpant the window proxy.
-            // We need to do this, because the Window and WindowProxy
-            // objects need to be in the same realm.
-            // JS_TransplantObject does this by copying the contents
-            // of the old window proxy to the new window proxy, then
-            // making the old window proxy a cross-realm wrapper
-            // pointing to the new window proxy.
+            // Brain transpant the window proxy. Brain transplantation is
+            // usually done to move a window proxy between compartments, but
+            // that's not what we are doing here. We need to do this just
+            // because we want to replace the wrapper's `ProxyTraps`, but we
+            // don't want to update its identity.
             rooted!(in(*cx) let new_js_proxy = NewWindowProxy(*cx, window_jsobject, handler));
             debug!(
                 "Transplanting proxy from {:p} to {:p}.",
diff --git a/tests/wpt/metadata/dom/events/event-global-extra.window.js.ini b/tests/wpt/metadata/dom/events/event-global-extra.window.js.ini
index 0759f69d170..29438998461 100644
--- a/tests/wpt/metadata/dom/events/event-global-extra.window.js.ini
+++ b/tests/wpt/metadata/dom/events/event-global-extra.window.js.ini
@@ -1,19 +1,4 @@
 [event-global-extra.window.html]
-  [window.event for constructors from another global: EventTarget]
-    expected: FAIL
-
-  [window.event for constructors from another global: XMLHttpRequest]
-    expected: FAIL
-
-  [window.event and element from another document]
-    expected: FAIL
-
-  [window.event and moving an element post-dispatch]
-    expected: FAIL
-
   [window.event should not be affected by nodes moving post-dispatch]
     expected: FAIL
 
-  [Listener from a different global]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/encoding/single-byte-decoder.html.ini b/tests/wpt/metadata/encoding/single-byte-decoder.html.ini
index 0de7a32529f..939a36eb9d9 100644
--- a/tests/wpt/metadata/encoding/single-byte-decoder.html.ini
+++ b/tests/wpt/metadata/encoding/single-byte-decoder.html.ini
@@ -2,7 +2,6 @@
   type: testharness
 
 [single-byte-decoder.html?document]
-  expected: TIMEOUT
   [ISO-8859-4: iso_8859-4:1988 (document.characterSet and document.inputEncoding)]
     expected: FAIL
 
@@ -30,9 +29,6 @@
   [ISO-8859-8: iso_8859-8:1988 (document.characterSet and document.inputEncoding)]
     expected: FAIL
 
-  [KOI8-R: cskoi8r (document.characterSet and document.inputEncoding)]
-    expected: TIMEOUT
-
 
 [single-byte-decoder.html?XMLHttpRequest]
   [ISO-8859-2: iso_8859-2:1987 (XMLHttpRequest)]
diff --git a/tests/wpt/metadata/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-return-value-handling-dynamic.html.ini b/tests/wpt/metadata/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-return-value-handling-dynamic.html.ini
index 87798a1d9c0..4c5287a46be 100644
--- a/tests/wpt/metadata/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-return-value-handling-dynamic.html.ini
+++ b/tests/wpt/metadata/html/browsers/browsing-the-web/navigating-across-documents/javascript-url-return-value-handling-dynamic.html.ini
@@ -5,15 +5,3 @@
   [Test javascript URL string return values in direct and indirect (target) frame contexts. 9]
     expected: FAIL
 
-  [Test javascript URL string return values in direct and indirect (target) frame contexts. 5]
-    expected: FAIL
-
-  [Test javascript URL string return values in direct and indirect (target) frame contexts. 6]
-    expected: FAIL
-
-  [Test javascript URL string return values in direct and indirect (target) frame contexts. 7]
-    expected: FAIL
-
-  [Test javascript URL string return values in direct and indirect (target) frame contexts. 8]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/browsers/origin/cross-origin-objects/cross-origin-objects-on-new-window.html.ini b/tests/wpt/metadata/html/browsers/origin/cross-origin-objects/cross-origin-objects-on-new-window.html.ini
deleted file mode 100644
index 735a9a75a2a..00000000000
--- a/tests/wpt/metadata/html/browsers/origin/cross-origin-objects/cross-origin-objects-on-new-window.html.ini
+++ /dev/null
@@ -1,2 +0,0 @@
-[cross-origin-objects-on-new-window.html]
-  expected: TIMEOUT
diff --git a/tests/wpt/metadata/html/browsers/sandboxing/sandbox-disallow-same-origin.html.ini b/tests/wpt/metadata/html/browsers/sandboxing/sandbox-disallow-same-origin.html.ini
deleted file mode 100644
index 90ccb850b41..00000000000
--- a/tests/wpt/metadata/html/browsers/sandboxing/sandbox-disallow-same-origin.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[sandbox-disallow-same-origin.html]
-  [Access to sandbox iframe is disallowed]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/creating_browsing_context_test_01.html.ini b/tests/wpt/metadata/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/creating_browsing_context_test_01.html.ini
index dec4c579137..16fa2c5cfc1 100644
--- a/tests/wpt/metadata/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/creating_browsing_context_test_01.html.ini
+++ b/tests/wpt/metadata/html/browsers/the-window-object/apis-for-creating-and-navigating-browsing-contexts-by-name/creating_browsing_context_test_01.html.ini
@@ -1,5 +1,4 @@
 [creating_browsing_context_test_01.html]
-  expected: TIMEOUT
   [first argument: absolute url]
-    expected: TIMEOUT
+    expected: FAIL
 
diff --git a/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-2.html.ini b/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-2.html.ini
index c6f45be1eb2..e63fe7c263e 100644
--- a/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-2.html.ini
+++ b/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_escaping-2.html.ini
@@ -1,5 +1,5 @@
 [iframe_sandbox_popups_escaping-2.html]
-  expected: TIMEOUT
+  expected: CRASH
   [Check that popups from a sandboxed iframe escape the sandbox if\n       allow-popups-to-escape-sandbox is used]
     expected: TIMEOUT
 
diff --git a/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-1.html.ini b/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-1.html.ini
index 9df1ac56f2a..963d4cd20ef 100644
--- a/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-1.html.ini
+++ b/tests/wpt/metadata/html/semantics/embedded-content/the-iframe-element/iframe_sandbox_popups_nonescaping-1.html.ini
@@ -1,6 +1,6 @@
 [iframe_sandbox_popups_nonescaping-1.html]
   type: testharness
-  expected: TIMEOUT
+  expected: CRASH
   [Check that popups from a sandboxed iframe do not escape the sandbox]
     expected: NOTRUN
 
diff --git a/tests/wpt/metadata/html/semantics/links/links-created-by-a-and-area-elements/htmlanchorelement_noopener.html.ini b/tests/wpt/metadata/html/semantics/links/links-created-by-a-and-area-elements/htmlanchorelement_noopener.html.ini
index 47d8a8e4cfe..a057142bbc5 100644
--- a/tests/wpt/metadata/html/semantics/links/links-created-by-a-and-area-elements/htmlanchorelement_noopener.html.ini
+++ b/tests/wpt/metadata/html/semantics/links/links-created-by-a-and-area-elements/htmlanchorelement_noopener.html.ini
@@ -1,6 +1,5 @@
 [htmlanchorelement_noopener.html]
   type: testharness
-  expected: TIMEOUT
   [Check that targeting of rel=noopener with a given name ignores an existing window with that name]
     expected: NOTRUN
 
@@ -14,5 +13,5 @@
     expected: FAIL
 
   [Check that rel=noopener with target=_self does a normal load]
-    expected: NOTRUN
+    expected: FAIL
 
diff --git a/tests/wpt/metadata/html/semantics/scripting-1/the-script-element/execution-timing/084.html.ini b/tests/wpt/metadata/html/semantics/scripting-1/the-script-element/execution-timing/084.html.ini
deleted file mode 100644
index d602b485be6..00000000000
--- a/tests/wpt/metadata/html/semantics/scripting-1/the-script-element/execution-timing/084.html.ini
+++ /dev/null
@@ -1,6 +0,0 @@
-[084.html]
-  type: testharness
-  expected: ERROR
-  [ scheduler: event listener defined by script in a removed IFRAME]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/webappapis/dynamic-markup-insertion/opening-the-input-stream/url-entry-document.window.js.ini b/tests/wpt/metadata/html/webappapis/dynamic-markup-insertion/opening-the-input-stream/url-entry-document.window.js.ini
deleted file mode 100644
index 6ac18f25c91..00000000000
--- a/tests/wpt/metadata/html/webappapis/dynamic-markup-insertion/opening-the-input-stream/url-entry-document.window.js.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[url-entry-document.window.html]
-  [document.open() changes document's URL to the entry settings object's responsible document's (through timeouts)]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-1.html.ini b/tests/wpt/metadata/html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-1.html.ini
index d0e9c948e3a..65334023f72 100644
--- a/tests/wpt/metadata/html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-1.html.ini
+++ b/tests/wpt/metadata/html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-1.html.ini
@@ -1,6 +1,3 @@
 [window-onerror-with-cross-frame-event-listeners-1.html]
   type: testharness
   bug: https://github.com/servo/servo/issues/3311
-  [The error event from an event listener should fire on that listener's global]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-4.html.ini b/tests/wpt/metadata/html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-4.html.ini
index eff06558b41..3d633ff0b60 100644
--- a/tests/wpt/metadata/html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-4.html.ini
+++ b/tests/wpt/metadata/html/webappapis/scripting/processing-model-2/window-onerror-with-cross-frame-event-listeners-4.html.ini
@@ -1,6 +1,3 @@
 [window-onerror-with-cross-frame-event-listeners-4.html]
   type: testharness
   bug: https://github.com/servo/servo/issues/3311
-  [The error event from an event listener should fire on that listener's global]
-    expected: FAIL
-
diff --git a/tests/wpt/metadata/wasm/jsapi/functions/entry-different-function-realm.html.ini b/tests/wpt/metadata/wasm/jsapi/functions/entry-different-function-realm.html.ini
index 20f3693b573..fa6e746f4cd 100644
--- a/tests/wpt/metadata/wasm/jsapi/functions/entry-different-function-realm.html.ini
+++ b/tests/wpt/metadata/wasm/jsapi/functions/entry-different-function-realm.html.ini
@@ -1,5 +1,4 @@
 [entry-different-function-realm.html]
-  expected: ERROR
   [Start function]
-    expected: TIMEOUT
+    expected: FAIL
 
diff --git a/tests/wpt/metadata/wasm/jsapi/functions/incumbent.html.ini b/tests/wpt/metadata/wasm/jsapi/functions/incumbent.html.ini
deleted file mode 100644
index 2b603de3c95..00000000000
--- a/tests/wpt/metadata/wasm/jsapi/functions/incumbent.html.ini
+++ /dev/null
@@ -1,5 +0,0 @@
-[incumbent.html]
-  expected: TIMEOUT
-  [Start function]
-    expected: TIMEOUT
-
diff --git a/tests/wpt/mozilla/meta/mozilla/cross-origin-objects/cross-origin-objects.html.ini b/tests/wpt/mozilla/meta/mozilla/cross-origin-objects/cross-origin-objects.html.ini
deleted file mode 100644
index 4f29d8c654b..00000000000
--- a/tests/wpt/mozilla/meta/mozilla/cross-origin-objects/cross-origin-objects.html.ini
+++ /dev/null
@@ -1,4 +0,0 @@
-[cross-origin-objects.html]
-  [Only whitelisted properties are accessible cross-origin]
-    expected: FAIL
-