Add observers to FrameSinkManagerHost.

content/browser/compositor/frame_sink_manager_host.h

Index: content/browser/compositor/frame_sink_manager_host.h
diff --git a/content/browser/compositor/frame_sink_manager_host.h b/content/browser/compositor/frame_sink_manager_host.h
index 8c7865ddbef16db670fc221000383d1d93c2663d..6d600e61223101b32f82acadfc514310eb56fef5 100644
--- a/content/browser/compositor/frame_sink_manager_host.h
+++ b/content/browser/compositor/frame_sink_manager_host.h
@@ -7,9 +7,11 @@
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
+#include "base/observer_list.h"
 #include "cc/ipc/frame_sink_manager.mojom.h"
 #include "cc/surfaces/frame_sink_id.h"
 #include "components/viz/frame_sinks/mojo_frame_sink_manager.h"
+#include "content/browser/compositor/frame_sink_observer.h"
 #include "content/common/content_export.h"
 #include "mojo/public/cpp/bindings/binding.h"
 
@@ -33,6 +35,9 @@ class CONTENT_EXPORT FrameSinkManagerHost
   // Start Mojo connection to FrameSinkManager. Most tests won't need this.
   void ConnectToFrameSinkManager();
 
+  void AddObserver(FrameSinkObserver* observer);
+  void RemoveObserver(FrameSinkObserver* observer);
+
   // See frame_sink_manager.mojom for descriptions.
   void CreateCompositorFrameSink(
       const cc::FrameSinkId& frame_sink_id,
@@ -59,6 +64,9 @@ class CONTENT_EXPORT FrameSinkManagerHost
   // happen using Mojo. See http://crbug.com/657959.
   viz::MojoFrameSinkManager frame_sink_manager_;
 
+  // Local observers to that receive OnSurfaceCreated() messages from IPC.
+  base::ObserverList<FrameSinkObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(FrameSinkManagerHost);
 };