WIP: Surface Synchronization System

cc/surfaces/pending_surface_observer.h

Index: cc/surfaces/pending_surface_observer.h
diff --git a/cc/surfaces/pending_surface_observer.h b/cc/surfaces/pending_surface_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..ae2c82134c8e3f00fcee7d5187918ca0433482aa
--- /dev/null
+++ b/cc/surfaces/pending_surface_observer.h
@@ -0,0 +1,31 @@
+// 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 CC_SURFACES_PENDING_SURFACE_OBSERVER_H_
+#define CC_SURFACES_PENDING_SURFACE_OBSERVER_H_
+
+#include "cc/surfaces/surface_id.h"
+
+namespace cc {
+
+using SurfaceDependencies = std::set<SurfaceId>;
+
+class Surface;
+
+class PendingSurfaceObserver {
+ public:
+  virtual void OnSurfaceActivated(Surface* pending_surface) = 0;
+  virtual void OnSurfaceChanged(
+      Surface* pending_surface,
+      const SurfaceDependencies& added_dependencies,
+      const SurfaceDependencies& removed_dependencies) = 0;
+  virtual void OnSurfaceDiscarded(Surface* pending_surface) = 0;
+
+ protected:
+  virtual ~PendingSurfaceObserver() {}
+};
+
+}  // namespace cc
+
+#endif  // CC_SURFACES_PENDING_SURFACE_OBSERVER_H_