Ensure SurfaceManager is only ever used from one thread.

cc/surfaces/surface_manager.h

Index: cc/surfaces/surface_manager.h
diff --git a/cc/surfaces/surface_manager.h b/cc/surfaces/surface_manager.h
index 202dfe3dde68bbda1fa92368683f56237bdec81b..7515be51fdaf2d9dac42cc388447428f4fb5bfb8 100644
--- a/cc/surfaces/surface_manager.h
+++ b/cc/surfaces/surface_manager.h
@@ -8,6 +8,7 @@
 #include "base/containers/hash_tables.h"
 #include "base/macros.h"
 #include "base/observer_list.h"
+#include "base/threading/thread_checker.h"
 #include "cc/surfaces/surface_damage_observer.h"
 #include "cc/surfaces/surface_id.h"
 #include "cc/surfaces/surfaces_export.h"
@@ -40,6 +41,7 @@ class CC_SURFACES_EXPORT SurfaceManager {
   typedef base::hash_map<SurfaceId, Surface*> SurfaceMap;
   SurfaceMap surface_map_;
   ObserverList<SurfaceDamageObserver> observer_list_;
+  base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(SurfaceManager);
 };