Sky should use an SkPicture when drawing

sky/compositor/display_delegate_bitmap.h

-// Copyright 2014 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 SKY_COMPOSITOR_DISPLAY_DELEGATE_BITMAP_H_
-#define SKY_COMPOSITOR_DISPLAY_DELEGATE_BITMAP_H_
-
-#include "sky/compositor/display_delegate.h"
-
-namespace sky {
-
-class LayerClient;
-
-class DisplayDelegateBitmap final : public DisplayDelegate {
- public:
-  explicit DisplayDelegateBitmap(LayerClient* client);
-  ~DisplayDelegateBitmap() override;
-
-  static DisplayDelegate* create(LayerClient* client);
-
-  void GetPixelsForTesting(std::vector<unsigned char>* pixels) override;
-  void Paint(mojo::GaneshSurface& surface, const gfx::Rect& size) override;
-
- private:
-  SkBitmap bitmap_;
-  LayerClient* client_;
-
-  DISALLOW_COPY_AND_ASSIGN(DisplayDelegateBitmap);
-};
-
-}  // namespace sky
-
-#endif  // SKY_COMPOSITOR_DISPLAY_DELEGATE_BITMAP_H_