Implement temporary reference assignment with DisplayCompositor.

services/ui/surfaces/display_compositor.cc

 // Copyright 2015 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.
 
 #include "services/ui/surfaces/display_compositor.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/memory/ptr_util.h"
@@ skipping 90 matching lines @@
     cc::mojom::MojoCompositorFrameSinkClientPtr client) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_EQ(0u, compositor_frame_sinks_.count(frame_sink_id));
 
   compositor_frame_sinks_[frame_sink_id] =
       base::MakeUnique<display_compositor::GpuCompositorFrameSink>(
           this, &manager_, frame_sink_id, std::move(request),
           std::move(private_request), std::move(client));
 }
 
+void DisplayCompositor::DropTemporaryReference(
+    const cc::SurfaceId& surface_id) {
+  manager_.DropTemporaryReference(surface_id);
+}
+
 std::unique_ptr<cc::Display> DisplayCompositor::CreateDisplay(
     const cc::FrameSinkId& frame_sink_id,
     gpu::SurfaceHandle surface_handle,
     cc::SyntheticBeginFrameSource* begin_frame_source) {
   scoped_refptr<cc::InProcessContextProvider> context_provider =
       new cc::InProcessContextProvider(
           gpu_service_, surface_handle, gpu_memory_buffer_manager_.get(),
           image_factory_, gpu::SharedMemoryLimits(),
           nullptr /* shared_context */);
 
@@ skipping 35 matching lines @@
 }
 
 void DisplayCompositor::DestroyCompositorFrameSink(cc::FrameSinkId sink_id) {
   compositor_frame_sinks_.erase(sink_id);
 }
 
 void DisplayCompositor::OnSurfaceCreated(const cc::SurfaceInfo& surface_info) {
   DCHECK(thread_checker_.CalledOnValidThread());
   DCHECK_GT(surface_info.device_scale_factor(), 0.0f);
 
+  // TODO(kylechar): |client_| will try to find an owner for the temporary
+  // reference to the new surface. With surface synchronization this might not

[Fady Samuel, 2017/02/24 18:07:38]

More details please? Why won't this be necessary, again? Is it because a parent
may have already claimed ownership?

[kylechar, 2017/02/28 18:07:15]

Done.

+  // be necessary in all cases, so we should let |client_| know if there is a
+  // temporary reference or not.
   if (client_)
     client_->OnSurfaceCreated(surface_info);
 }
 
 void DisplayCompositor::OnSurfaceDamaged(const cc::SurfaceId& surface_id,
                                          bool* changed) {}
 
 }  // namespace ui