Use a union typdef for the return type of canvas.getContext

third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.h

Index: third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.h
diff --git a/third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.h b/third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.h
new file mode 100644
index 0000000000000000000000000000000000000000..bacb33cc0ef181118c9714b5c4deb01fe3feb435
--- /dev/null
+++ b/third_party/WebKit/Source/modules/canvas/HTMLCanvasElementModule.h
@@ -0,0 +1,25 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef HTMLCanvasElementModule_h
+#define HTMLCanvasElementModule_h
+
+#include "core/html/HTMLCanvasElement.h"
+#include "wtf/text/WTFString.h"
+
+namespace blink {
+
+class CanvasContextCreationAttributes;
+class HTMLCanvasElement;
+class ScriptState;
+
+class HTMLCanvasElementModule {
+    STATIC_ONLY(HTMLCanvasElementModule);
+public:
+    static void getContext(HTMLCanvasElement&, const String&, const CanvasContextCreationAttributes&, RenderingContext&);
+};
+
+}
+
+#endif