Allow AllocateGpuMemoryBuffer to be called from multiple threads.

content/browser/renderer_host/render_message_filter.h

Index: content/browser/renderer_host/render_message_filter.h
diff --git a/content/browser/renderer_host/render_message_filter.h b/content/browser/renderer_host/render_message_filter.h
index 764bf31259bf69345bcbbbfe6fe3e664d7774901..ff370077b4afe42a72f40a7b52c788e4a2127029 100644
--- a/content/browser/renderer_host/render_message_filter.h
+++ b/content/browser/renderer_host/render_message_filter.h
@@ -9,6 +9,10 @@
 #include <windows.h>
 #endif
 
+#if defined(OS_MACOSX)
+#include <queue>
+#endif
+
 #include <set>
 #include <string>
 #include <vector>
@@ -306,7 +310,7 @@ class RenderMessageFilter : public BrowserMessageFilter {
   MediaInternals* media_internals_;
 
 #if defined(OS_MACOSX)
-  base::ScopedCFTypeRef<CFTypeRef> last_io_surface_;
+  std::queue<base::ScopedCFTypeRef<CFTypeRef> > io_surfaces_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(RenderMessageFilter);