Changing return value of request animation frame.

lib/html/idl/dart/dart.idl

 
 // This file introduces / supplements and forces Dart declarations.
 
 module default {
   // TODO(efortuna): Clean up these comments once we have dealt with the extra
   // methods on these list-like classes.
   ClientRectList implements sequence<ClientRect>;
   CSSRuleList implements sequence<CSSRule>;
   CSSValueList implements sequence<CSSValue>;
   DOMMimeTypeArray implements sequence<DOMMimeType>; // has namedItem field.
@@ skipping 384 matching lines @@
     // Suppress the default since it has non-standard return type and add
     // overrides.
     [Suppressed] boolean send(in DOMString data) raises(DOMException);
     [Custom] void send(DOMString data) raises(DOMException);
     [Custom] void send(Blob data) raises(DOMException);
     [Custom] void send(ArrayBuffer data) raises(DOMException);
     [Custom] void send(ArrayBufferView data) raises(DOMException);
   };
 }
 
+module core {
+  [supplemental, Callback]
+  interface RequestAnimationFrameCallback {
+    // Webkit implements this as returning bool, but standard is void.
+    [Suppressed] boolean handleEvent(in DOMTimeStamp time);
+    void handleEvent(in DOMTimeStamp time);
+  };
+}