Add rendering context and rendering 2D context to OffscreenCanvas

third_party/WebKit/Source/modules/offscreencanvas/OffscreenCanvasRenderingContext.cpp

+// 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.
+
+#include "modules/offscreencanvas/OffscreenCanvasRenderingContext.h"
+
+namespace blink {
+
+OffscreenCanvasRenderingContext::OffscreenCanvasRenderingContext(OffscreenCanvas* canvas)
+    : m_offscreenCanvas(canvas)
+{
+}
+
+OffscreenCanvasRenderingContext::ContextType OffscreenCanvasRenderingContext::contextTypeFromId(const String& id)
+{
+    if (id == "2d")
+        return Context2d;
+    if (id == "webgl")
+        return ContextWebgl;
+    if (id == "webgl2")
+        return ContextWebgl2;
+    return ContextTypeCount;
+}
+
+DEFINE_TRACE(OffscreenCanvasRenderingContext)
+{
+    visitor->trace(m_offscreenCanvas);
+}
+
+} // namespace blink