Add FrameGenerator Unit Tests

services/ui/ws/display_client_compositor_frame_sink.h

 // Copyright 2017 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 SERVICES_UI_PUBLIC_CPP_DISPLAY_CLIENT_COMPOSITOR_FRAME_SINK_H_
 #define SERVICES_UI_PUBLIC_CPP_DISPLAY_CLIENT_COMPOSITOR_FRAME_SINK_H_
 
 #include "cc/ipc/display_compositor.mojom.h"
 #include "cc/ipc/mojo_compositor_frame_sink.mojom.h"
 #include "cc/output/compositor_frame_sink.h"
 #include "cc/scheduler/begin_frame_source.h"
 #include "cc/surfaces/local_surface_id.h"
 #include "cc/surfaces/local_surface_id_allocator.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "ui/gfx/geometry/size.h"
 
 namespace base {
 class ThreadChecker;
 }  // namespace base
 
 namespace ui {
 namespace ws {
 
+// DisplayClientCompositorFrameSink submits CompositorFrames to a
+// MojoCompositorFrameSink, with the client's frame being the root surface of
+// the Display.
 class DisplayClientCompositorFrameSink
     : public cc::CompositorFrameSink,
       public cc::mojom::MojoCompositorFrameSinkClient,
       public cc::ExternalBeginFrameSourceClient {
  public:
   DisplayClientCompositorFrameSink(
       const cc::FrameSinkId& frame_sink_id,
       cc::mojom::MojoCompositorFrameSinkAssociatedPtr compositor_frame_sink,
       cc::mojom::DisplayPrivateAssociatedPtr display_private,
       cc::mojom::MojoCompositorFrameSinkClientRequest client_request);
@@ skipping 28 matching lines @@
   std::unique_ptr<cc::ExternalBeginFrameSource> begin_frame_source_;
   const cc::FrameSinkId frame_sink_id_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayClientCompositorFrameSink);
 };
 
 }  // namspace ws
 }  // namespace ui
 
 #endif  // SERVICES_UI_PUBLIC_CPP_DISPLAY_CLIENT_COMPOSITOR_FRAME_SINK_H_