Implement canvas focus ring methods.

Source/core/html/canvas/CanvasRenderingContext2D.idl

 /*
  * Copyright (C) 2006 Apple Computer, 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
  *    notice, this list of conditions and the following disclaimer in the
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     [RaisesException] ImageData createImageData(float sw, float sh);
 
     [Custom] attribute custom strokeStyle;
     [Custom] attribute custom fillStyle;
 
     // pixel manipulation
     [RaisesException] ImageData getImageData(float sx, float sy, float sw, float sh);
 
     [RaisesException] ImageData webkitGetImageDataHD(float sx, float sy, float sw, float sh);
 
+    // Focus rings
+    [EnabledAtRuntime=experimentalCanvasFeatures] void drawSystemFocusRing(Element element);
+    [EnabledAtRuntime=experimentalCanvasFeatures] boolean drawCustomFocusRing(Element element);
+
     readonly attribute float webkitBackingStorePixelRatio;
 
     attribute boolean webkitImageSmoothingEnabled;
 
     [EnabledAtRuntime=experimentalCanvasFeatures] Canvas2DContextAttributes getContextAttributes();
 };