Make atob() / btoa() argument non optional

Source/core/page/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 162 matching lines @@
     [EnabledAtRuntime=experimentalCanvasFeatures, RaisesException] void createImageBitmap(ImageData data, ImageBitmapCallback callback, long sx, long sy, long sw, long sh);
     [EnabledAtRuntime=experimentalCanvasFeatures, RaisesException] void createImageBitmap(ImageBitmap bitmap, ImageBitmapCallback callback);
     [EnabledAtRuntime=experimentalCanvasFeatures, RaisesException] void createImageBitmap(ImageBitmap bitmap, ImageBitmapCallback callback, long sx, long sy, long sw, long sh);
 
     [MeasureAs=UnprefixedRequestAnimationFrame] long requestAnimationFrame(RequestAnimationFrameCallback callback);
     void cancelAnimationFrame(long id);
     [MeasureAs=PrefixedRequestAnimationFrame] long webkitRequestAnimationFrame(RequestAnimationFrameCallback callback);
     [ImplementedAs=cancelAnimationFrame] void webkitCancelAnimationFrame(long id);
     [ImplementedAs=cancelAnimationFrame] void webkitCancelRequestAnimationFrame(long id); // This is a deprecated alias for webkitCancelAnimationFrame(). Remove this when removing vendor prefix.
 
-    // Base64
-    [RaisesException] DOMString atob([TreatNullAs=NullString,Default=Undefined] optional DOMString string);
-    [RaisesException] DOMString btoa([TreatNullAs=NullString,Default=Undefined] optional DOMString string);
-
     [Replaceable] readonly attribute CSS CSS;
 
     // Events
     attribute EventListener onabort;
     attribute EventListener onbeforeunload;
     attribute EventListener onblur;
     attribute EventListener oncanplay;
     attribute EventListener oncanplaythrough;
     attribute EventListener onchange;
     attribute EventListener onclick;
@@ skipping 111 matching lines @@
     [Conditional=WEB_AUDIO] attribute PannerNodeConstructor webkitAudioPannerNode;
 
     // window.toString() requires special handling in V8
     [DoNotCheckSignature, DoNotCheckSecurity, Custom, NotEnumerable] DOMString toString();
 
     [ImplementedAs=anonymousIndexedGetter, NotEnumerable] getter Window(unsigned long index);
     [Custom, NotEnumerable] getter Window (DOMString name);
 };
 
 Window implements WindowTimers;
-
+Window implements WindowBase64;