Use dictionaries for context creation attributes. Eliminate custom bindings.

Source/core/html/HTMLCanvasElement.h

Index: Source/core/html/HTMLCanvasElement.h
diff --git a/Source/core/html/HTMLCanvasElement.h b/Source/core/html/HTMLCanvasElement.h
index 60a1a606b259de724848dd38c51d0fb124517c08..00915d93782abcf344fa291b417543920ab6cfe0 100644
--- a/Source/core/html/HTMLCanvasElement.h
+++ b/Source/core/html/HTMLCanvasElement.h
@@ -28,6 +28,7 @@
 #ifndef HTMLCanvasElement_h
 #define HTMLCanvasElement_h
 
+#include "bindings/core/v8/UnionTypesCore.h"
 #include "core/dom/Document.h"
 #include "core/html/HTMLElement.h"
 #include "core/html/canvas/CanvasImageSource.h"
@@ -44,7 +45,7 @@
 namespace blink {
 
 class AffineTransform;
-class CanvasContextAttributes;
+class CanvasContextCreationAttributes;
 class CanvasRenderingContext;
 class GraphicsContext;
 class GraphicsContextStateSaver;
@@ -100,7 +101,7 @@ public:
         reset();
     }
 
-    CanvasRenderingContext* getContext(const String&, CanvasContextAttributes* attributes = 0);
+    void getContext(const String&, const CanvasContextCreationAttributes&, CanvasRenderingContext2DOrWebGLRenderingContext& result);
     bool isPaintable() const;
 
     static String toEncodingMimeType(const String& mimeType);