Decouple GpuCompositorFrameSink from DisplayCompositor

components/display_compositor/gpu_compositor_frame_sink_delegate.h

Index: components/display_compositor/gpu_compositor_frame_sink_delegate.h
diff --git a/components/display_compositor/gpu_compositor_frame_sink_delegate.h b/components/display_compositor/gpu_compositor_frame_sink_delegate.h
new file mode 100644
index 0000000000000000000000000000000000000000..7297f39ed0e264397165f545e6b6b35282037c85
--- /dev/null
+++ b/components/display_compositor/gpu_compositor_frame_sink_delegate.h
@@ -0,0 +1,26 @@
+// 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 COMPONENTS_DISPLAY_COMPOSITOR_GPU_COMPOSITOR_FRAME_SINK_DELEGATE_H_
+#define COMPONENTS_DISPLAY_COMPOSITOR_GPU_COMPOSITOR_FRAME_SINK_DELEGATE_H_
+
+namespace display_compositor {
+
+class GpuCompositorFrameSinkDelegate {
+ public:
+  // We must avoid destroying a GpuCompositorFrameSink until both the display
+  // compositor host and the client drop their connection to avoid getting into
+  // a state where surfaces references are inconsistent.
+  virtual void OnClientConnectionLost(const cc::FrameSinkId& frame_sink_id,
+                                      bool destroy_compositor_frame_sink) = 0;
+  virtual void OnPrivateConnectionLost(const cc::FrameSinkId& frame_sink_id,
+                                       bool destroy_compositor_frame_sink) = 0;
+
+ protected:
+  virtual ~GpuCompositorFrameSinkDelegate() {}
+};
+
+}  // namespace display_compositor
+
+#endif  // COMPONENTS_DISPLAY_COMPOSITOR_GPU_COMPOSITOR_FRAME_SINK_DELEGATE_H_