style: Simplify Owned FFI types.

And make them actually sound. We're defining functions on Rust-land that get
structs as arguments, but declaring them in C++ as getting pointers.

This is another step in order to be able to autogenerate ServoBindings.h and
remove bindings.rs altogether.

We remove FooOwned in favor of Owned<Foo>, which is generated via cbindgen.

It'd be good to actually mark Owned and such as MOZ_MUST_USE_TYPE, so I sent
https://github.com/eqrion/cbindgen/pull/307 for that.

Differential Revision: https://phabricator.services.mozilla.com/D24681

components/style/build_gecko.rs

@@ -258,13 +258,6 @@ mod bindings {
             .collect()
     }
 
-    fn get_boxed_types() -> Vec<String> {
-        get_types("ServoBoxedTypeList.h", "SERVO_BOXED_TYPE")
-            .into_iter()
-            .map(|(_, type_name)| type_name)
-            .collect()
-    }
-
     struct BuilderWithConfig<'a> {
         builder: Builder,
         config: &'a Table,
@@ -453,22 +446,6 @@ mod bindings {
                     ty
                 ));
         }
-        for ty in get_boxed_types().iter() {
-            builder = builder
-                .blacklist_type(format!("{}Owned", ty))
-                .raw_line(format!(
-                    "pub type {0}Owned = ::gecko_bindings::sugar::ownership::Owned<{0}>;",
-                    ty
-                ))
-                .blacklist_type(format!("{}OwnedOrNull", ty))
-                .raw_line(format!(
-                    concat!(
-                        "pub type {0}OwnedOrNull = ",
-                        "::gecko_bindings::sugar::ownership::OwnedOrNull<{0}>;"
-                    ),
-                    ty
-                ));
-        }
         write_binding_file(builder, BINDINGS_FILE, &fixups);
     }
 

components/style/cbindgen.toml

@@ -109,6 +109,8 @@ include = [
   "WillChangeBits",
   "TextDecorationLine",
   "MozListReversed",
+  "Owned",
+  "OwnedOrNull",
 ]
 item_types = ["enums", "structs", "typedefs"]
 
@@ -208,3 +210,21 @@ item_types = ["enums", "structs", "typedefs"]
   static inline StyleRestyleHint RecascadeSubtree();
   static inline StyleRestyleHint ForAnimations();
 """
+
+# TODO(emilio): Add hooks to cbindgen to be able to generate MOZ_MUST_USE_TYPE
+# or MOZ_MUST_USE on the functions.
+"Owned" = """
+  UniquePtr<GeckoType> Consume() {
+    UniquePtr<GeckoType> ret(ptr);
+    ptr = nullptr;
+    return ret;
+  }
+"""
+
+"OwnedOrNull" = """
+  UniquePtr<GeckoType> Consume() {
+    UniquePtr<GeckoType> ret(ptr);
+    ptr = nullptr;
+    return ret;
+  }
+"""

components/style/gecko_bindings/sugar/ownership.rs

@@ -320,27 +320,6 @@ impl<GeckoType> OwnedOrNull<GeckoType> {
         self.ptr.is_null()
     }
 
-    /// Returns an owned pointer if this is non-null, and `None` otherwise.
-    pub fn into_box_opt<ServoType>(self) -> Option<Box<ServoType>>
-    where
-        ServoType: HasBoxFFI<FFIType = GeckoType>,
-    {
-        if self.is_null() {
-            None
-        } else {
-            Some(unsafe { transmute(self) })
-        }
-    }
-
-    /// Returns an `Owned<GeckoType>` if non-null, `None` otherwise.
-    pub fn into_owned_opt(self) -> Option<Owned<GeckoType>> {
-        if self.is_null() {
-            None
-        } else {
-            Some(unsafe { transmute(self) })
-        }
-    }
-
     /// Gets a immutable reference to the underlying Gecko type, or `None` if
     /// null.
     pub fn borrow(&self) -> Option<&GeckoType> {