Add some plumbing for the color management of canvases

third_party/WebKit/Source/modules/offscreencanvas2d/OffscreenCanvasRenderingContext2D.h

 // 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 OffscreenCanvasRenderingContext2D_h
 #define OffscreenCanvasRenderingContext2D_h
 
 #include "core/html/canvas/CanvasContextCreationAttributes.h"
 #include "core/html/canvas/CanvasRenderingContext.h"
 #include "core/html/canvas/CanvasRenderingContextFactory.h"
@@ skipping 51 matching lines @@
 
     AffineTransform baseTransform() const final;
     void didDraw(const SkIRect& dirtyRect) final;
 
     bool stateHasFilter() final;
     SkImageFilter* stateGetFilter() final;
     void snapshotStateForFilter() final { }
 
     void validateStateStack() final;
 
-    bool hasAlpha() const override { return m_hasAlpha; }
+    bool hasAlpha() const final { return CanvasRenderingContext::hasAlpha(); }
     bool isContextLost() const override;
 
     ImageBitmap* transferToImageBitmap(ExceptionState&) final;
 
 protected:
     OffscreenCanvasRenderingContext2D(ScriptState*, OffscreenCanvas*, const CanvasContextCreationAttributes& attrs);
     DECLARE_VIRTUAL_TRACE();
 
 private:
-    bool m_hasAlpha;
     bool m_needsMatrixClipRestore = false;
     std::unique_ptr<ImageBuffer> m_imageBuffer;
 };
 
 } // namespace blink
 
 #endif // OffscreenCanvasRenderingContext2D_h