Improve the declared IDL type for postMessage()'s transferables

Source/core/frame/Window.idl

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 148 matching lines @@
     [RuntimeEnabled=LocalStorage, LogActivity=GetterOnly, RaisesException=Getter] readonly attribute Storage localStorage;
 
     // This is the interface orientation in degrees. Some examples are:
     //  0 is straight up; -90 is when the device is rotated 90 clockwise;
     //  90 is when rotated counter clockwise.
     [RuntimeEnabled=OrientationEvent, MeasureAs=WindowOrientation] readonly attribute long orientation;
 
     [Replaceable] readonly attribute Console console;
 
     // cross-document messaging
-    [DoNotCheckSecurity, Custom, RaisesException] void postMessage(SerializedScriptValue message, DOMString targetOrigin, optional MessagePort[] messagePorts);
+    [DoNotCheckSecurity, Custom, RaisesException] void postMessage(SerializedScriptValue message, DOMString targetOrigin, optional sequence<Transferable> transfer);
 
     [Replaceable] readonly attribute Performance performance;
 
     [MeasureAs=UnprefixedRequestAnimationFrame] long requestAnimationFrame(RequestAnimationFrameCallback callback);
     void cancelAnimationFrame(long id);
     [DeprecateAs=PrefixedRequestAnimationFrame] long webkitRequestAnimationFrame(RequestAnimationFrameCallback callback);
     [DeprecateAs=PrefixedCancelAnimationFrame, ImplementedAs=cancelAnimationFrame] void webkitCancelAnimationFrame(long id);
     [DeprecateAs=PrefixedCancelRequestAnimationFrame, ImplementedAs=cancelAnimationFrame] void webkitCancelRequestAnimationFrame(long id);
 
     [Replaceable] readonly attribute CSS CSS;
@@ skipping 24 matching lines @@
     [MeasureAs=PrefixedWindowURL] attribute URLConstructor webkitURL; // FIXME: deprecate this.
     [MeasureAs=PrefixedMutationObserverConstructor] attribute MutationObserverConstructor WebKitMutationObserver;
 
     // window.toString() requires special handling in V8
     [DoNotCheckSignature, DoNotCheckSecurity, Custom, NotEnumerable] stringifier;
 
     [NotEnumerable] getter Window (unsigned long index);
     [Custom, NotEnumerable] getter Window (DOMString name);
 };
 
+// http://www.whatwg.org/specs/web-apps/current-work/#transferable-objects
+//
+// Expressing the Transferable typedef in IDL depends on http://crbug.com/240176.
+// The postMessage() methods taking a Transferable array argument have custom
+// binding code that is able to handle the Transferables that we currently
+// recognize. To be able to declare a postMessage() signature that matches
+// the implementation, we provide a Transferable typedef but with an
+// incomplete type.
+//
+// FIXME: make this typedef accurate once enough of http://crbug.com/240176
+// is in place.
+// FIXME: consider putting this typedef in an .idl file containing spec-wide
+// utility type definitions.
+typedef MessagePort Transferable;
+
 Window implements GlobalEventHandlers;
 Window implements WindowBase64;
 Window implements WindowEventHandlers;
 Window implements WindowTimers;