zero-copy: Clarify to allocate/destroy GpuMemoryBuffer on any thread and use it on the main thread o

ui/ozone/platform/caca/caca_window_manager.h

Index: ui/ozone/platform/caca/caca_window_manager.h
diff --git a/ui/ozone/platform/caca/caca_window_manager.h b/ui/ozone/platform/caca/caca_window_manager.h
index 4f51a7f102161464be079d6ccd592b4ba44a8908..3113496542f1707ee8aa13e4fcc1ae5a34a3527b 100644
--- a/ui/ozone/platform/caca/caca_window_manager.h
+++ b/ui/ozone/platform/caca/caca_window_manager.h
@@ -7,6 +7,7 @@
 
 #include "base/id_map.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/threading/thread_checker.h"
 #include "ui/ozone/public/surface_factory_ozone.h"
 
 namespace gfx {
@@ -37,6 +38,7 @@ class CacaWindowManager : public SurfaceFactoryOzone {
 
  private:
   IDMap<CacaWindow> windows_;
+  base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(CacaWindowManager);
 };