Bug 1516366 - Move mExpandoAndGeneration from nsDocument to nsIDocument. r=smaug

Now that bindgen can represent it properly (bug 1516365) we can do this.

Differential Revision: https://phabricator.services.mozilla.com/D15357

dom/base/nsDocument.h

@@ -173,13 +173,6 @@ class nsDocument : public nsIDocument {
   virtual ~nsDocument();
 
  public:
-  // FIXME(emilio): This needs to be here instead of in nsIDocument because Rust
-  // can't represent alignas(8) values on 32-bit architectures, which would
-  // cause nsIDocument's layout to be wrong in the Rust side.
-  //
-  // This can be fixed after updating to rust 1.25 and updating bindgen to
-  // include https://github.com/rust-lang-nursery/rust-bindgen/pull/1271.
-  js::ExpandoAndGeneration mExpandoAndGeneration;
 
   friend class nsCallRequestFullscreen;
 

dom/base/nsIDocument.h

@@ -4418,6 +4418,10 @@ class nsIDocument : public nsINode,
 
   // Pres shell resolution saved before entering fullscreen mode.
   float mSavedResolution;
+
+ public:
+  // Needs to be public because the bindings code pokes at it.
+  js::ExpandoAndGeneration mExpandoAndGeneration;
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsIDocument, NS_IDOCUMENT_IID)

layout/style/ServoBindings.toml

@@ -49,11 +49,6 @@ hide-types = [
     "nsString",
     ".*char_traits",
     ".*incompatible_char_type",
-    # JS::Value uses alignas(8) which bindgen can't represent correctly on Linux
-    # 32-bit.  See https://github.com/rust-lang-nursery/rust-bindgen/issues/917.
-    # It's also not used by Stylo.  The following types are also hidden for
-    # making use of it and being similarly unused by Stylo.
-    "JS::Value",
     "mozilla::binding_danger::TErrorResult.*",
     "mozilla::ErrorResult.*", # Causes JSWhyMagic to be included & handled incorrectly.
     "mozilla::dom::CallbackFunction",