Make cc/paint have concrete types

third_party/WebKit/Source/platform/graphics/gpu/AcceleratedImageBufferSurface.h

 /*
  * Copyright (c) 2013, Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 35 matching lines @@
   WTF_MAKE_NONCOPYABLE(AcceleratedImageBufferSurface);
   USING_FAST_MALLOC(AcceleratedImageBufferSurface);
 
  public:
   AcceleratedImageBufferSurface(const IntSize&,
                                 OpacityMode = NonOpaque,
                                 sk_sp<SkColorSpace> = nullptr,
                                 SkColorType = kN32_SkColorType);
   ~AcceleratedImageBufferSurface() override {}
 
-  PaintCanvas* canvas() override {
-    return m_surface ? m_surface->getCanvas() : nullptr;
-  }
+  PaintCanvas* canvas() override { return m_canvas.get(); }
   bool isValid() const override;
   bool isAccelerated() const override { return true; }
   sk_sp<SkImage> newImageSnapshot(AccelerationHint, SnapshotReason) override;
   GLuint getBackingTextureHandleForOverwrite() override;
 
  private:
   unsigned m_contextId;
-  sk_sp<PaintSurface> m_surface;  // Uses m_contextProvider.
+  sk_sp<SkSurface> m_surface;  // Uses m_contextProvider.
+  std::unique_ptr<PaintCanvas> m_canvas;
 };
 
 }  // namespace blink
 
 #endif