cc: Clean up OutputSurfaceClient.

cc/output/output_surface.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_H_
 #define CC_OUTPUT_OUTPUT_SURFACE_H_
 
 #include <deque>
 #include <memory>
 
@@ skipping 100 matching lines @@
                        const gfx::ColorSpace& color_space,
                        bool has_alpha) = 0;
 
   virtual bool HasExternalStencilTest() const = 0;
   virtual void ApplyExternalStencil() = 0;
 
   // Gives the GL internal format that should be used for calling CopyTexImage2D
   // when the framebuffer is bound via BindFramebuffer().
   virtual uint32_t GetFramebufferCopyTextureFormat() = 0;
 
-  // The implementation may destroy or steal the contents of the CompositorFrame
-  // passed in (though it will not take ownership of the CompositorFrame
-  // itself). For successful swaps, the implementation must call
-  // OutputSurfaceClient::DidSwapBuffersComplete() eventually.
+  // Swaps the current backbuffer to the screen. For successful swaps, the
+  // implementation must call OutputSurfaceClient::DidReceiveSwapBuffersAck()
+  // after returning from this method in order to unblock the next frame.
   virtual void SwapBuffers(OutputSurfaceFrame frame) = 0;
 
  protected:
   // Used internally for the context provider to inform the client about loss,
   // and can be overridden to change behaviour instead of informing the client.
   virtual void DidLoseOutputSurface();
 
   OutputSurfaceClient* client_ = nullptr;
 
   struct OutputSurface::Capabilities capabilities_;
   scoped_refptr<ContextProvider> context_provider_;
   scoped_refptr<VulkanContextProvider> vulkan_context_provider_;
   std::unique_ptr<SoftwareOutputDevice> software_device_;
   base::ThreadChecker thread_checker_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(OutputSurface);
 };
 
 }  // namespace cc
 
 #endif  // CC_OUTPUT_OUTPUT_SURFACE_H_