Expose FontFaceSetLoadEvent and add a constructor for it

third_party/WebKit/Source/core/css/FontFaceSetLoadEvent.idl

Index: third_party/WebKit/Source/core/css/FontFaceSetLoadEvent.idl
diff --git a/third_party/WebKit/Source/core/css/FontFaceSetLoadEvent.idl b/third_party/WebKit/Source/core/css/FontFaceSetLoadEvent.idl
index 201f53c25f1361ec62b60cf17ddbafc0f3f41f40..caa58573b072452df191539eefac1332d9fb80c7 100644
--- a/third_party/WebKit/Source/core/css/FontFaceSetLoadEvent.idl
+++ b/third_party/WebKit/Source/core/css/FontFaceSetLoadEvent.idl
@@ -30,10 +30,10 @@
 
 // https://dev.w3.org/csswg/css-font-loading/#fontfacesetloadevent
 
-// TODO(foolip): This interface should have a constructor and
-// [Exposed=Window,Worker], and thus not [NoInterfaceObject].
 [
-    NoInterfaceObject,
+  Constructor(DOMString type, optional FontFaceSetLoadEventInit eventInitDict),
+  // TODO(lunalu): Exposed=(Window,Worker)
+  Exposed=Window
 ] interface FontFaceSetLoadEvent : Event {
-    readonly attribute sequence<FontFace> fontfaces;
+    [SameObject, SaveSameObject] readonly attribute FrozenArray<FontFace> fontfaces;

[haraken, 2016/12/21 00:13:49]

[SaveSameObject] is a hack to optimize performance. Unless this is really
performance-sensitive, you can drop the IDL extended attribute. Then you can
also drop the change in V8PrivateProperty.

[lunalu1, 2016/12/21 18:51:32]

Done.

[foolip, 2017/01/02 16:55:35]

Is it not needed to get the event.fontfaces===event.fontfaces behavior right?

 };