Use surface copy requests for layout tests.

content/renderer/layout_test_dependencies.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 CONTENT_RENDER_LAYOUT_TEST_DEPENDENCIES_H_
 #define CONTENT_RENDER_LAYOUT_TEST_DEPENDENCIES_H_
 
 #include <stdint.h>
 #include <memory>
 
 #include "base/memory/ref_counted.h"
 
 namespace cc {
 class ContextProvider;
+class CopyOutputRequest;
 class OutputSurface;
+class SwapPromise;
 }
 
 namespace gpu {
 class GpuChannelHost;
 }
 
 namespace content {
 class CompositorDependencies;
 
 // This class allows injection of LayoutTest-specific behaviour to the
 // RenderThreadImpl.
 class LayoutTestDependencies {
  public:
   virtual std::unique_ptr<cc::OutputSurface> CreateOutputSurface(
+      int32_t routing_id,
       scoped_refptr<gpu::GpuChannelHost> gpu_channel,
       scoped_refptr<cc::ContextProvider> compositor_context_provider,
       scoped_refptr<cc::ContextProvider> worker_context_provider,
       CompositorDependencies* deps) = 0;
+
+  // Returns a SwapPromise which should be queued for the appropriate frame.

[danakj, 2016/07/22 20:50:26]

appropriate = the next compositor frame?

[jbroman, 2016/07/25 18:50:55]

Technically no (you could hold on to this and wait until the frame you want to
take a screenshot), but in practice yes, so I'll change the comment as you
suggested.

+  virtual std::unique_ptr<cc::SwapPromise> RequestCopyOfOutput(
+      int32_t routing_id,
+      std::unique_ptr<cc::CopyOutputRequest> request) = 0;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDER_LAYOUT_TEST_DEPENDENCIES_H_