cc: Add OutputSurface state snapshots.

cc/output/output_surface_client.h

 // Copyright 2012 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 CC_OUTPUT_OUTPUT_SURFACE_CLIENT_H_
 #define CC_OUTPUT_OUTPUT_SURFACE_CLIENT_H_
 
 #include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/time/time.h"
 #include "cc/base/cc_export.h"
 #include "cc/output/context_provider.h"
 #include "cc/resources/returned_resource.h"
 #include "gpu/command_buffer/common/texture_in_use_response.h"
+#include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/geometry/rect.h"
 
 namespace gfx {
 class Transform;
 }
 
 namespace cc {
 
 class BeginFrameSource;
 struct ManagedMemoryPolicy;
 
 class CC_EXPORT OutputSurfaceClient {
  public:
   // A notification that the swap of the backbuffer to the hardware is complete
   // and is now visible to the user.
   virtual void DidReceiveSwapBuffersAck() = 0;
 
   // For surfaceless/ozone implementations to create damage for the next frame.
   virtual void SetNeedsRedrawRect(const gfx::Rect& damage_rect) = 0;
 
   // For overlays.
   virtual void DidReceiveTextureInUseResponses(
       const gpu::TextureInUseResponses& responses) = 0;
 
+  // Readback the contents of last swapped overlay textures.
+  virtual void ReadbackSwappedOverlayTextures(
+      std::vector<SkBitmap>* bitmaps,

[danakj, 2016/11/01 23:33:01]

why not a parameter of the Callback?

[reveman, 2016/11/02 00:37:05]

It just evolved this way. I guess the alternative is to pass
std::unique_ptr<std::vector<SkBitmap>> with this callback and
std::unique_ptr<SkBitmap> with the framebuffer version but it seemed a bit
easier to just allocate these objects upfront and the buffer queue and
outputsurface fill them in. Let me know if you prefer that or have a better idea
for how to do this.

+      const base::Callback<void(bool)>& callback) = 0;
+
  protected:
   virtual ~OutputSurfaceClient() {}
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OUTPUT_SURFACE_CLIENT_H_