Add iterator support to FontFaceSet

Source/core/css/FontFaceSet.idl

Index: Source/core/css/FontFaceSet.idl
diff --git a/Source/core/css/FontFaceSet.idl b/Source/core/css/FontFaceSet.idl
index 31ae4fc8d0cc9d2c446b0967cc8dbe1a3f4a72ee..526b7e1d0d0fc677e857f5c90c75d2e4826bbb37 100644
--- a/Source/core/css/FontFaceSet.idl
+++ b/Source/core/css/FontFaceSet.idl
@@ -32,6 +32,7 @@ enum FontFaceSetLoadStatus { "loading", "loaded" };
 
 [
     ActiveDOMObject,
+    Iterable,
     SetWrapperReferenceFrom=document,
     NoInterfaceObject,
 ] interface FontFaceSet : EventTarget {
@@ -49,6 +50,9 @@ enum FontFaceSetLoadStatus { "loading", "loaded" };
     [RaisesException, ImplementedAs=remove] boolean delete(FontFace fontFace);
     void forEach(FontFaceSetForEachCallback callback, optional any thisArg);
     [RaisesException] boolean has(FontFace fontFace);
+    Iterator keys();
+    Iterator values();
+    Iterator entries();
 
     readonly attribute unsigned long size;
     readonly attribute FontFaceSetLoadStatus status;