gpu: Add IOSurface backed GpuMemoryBuffer implementation.

content/renderer/render_thread_impl.h

Index: content/renderer/render_thread_impl.h
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index 1f16ee7d9302e5d6627375986e45bfa8f2f516f3..7a3f20cd6f3f8954a71e3c5a13dc4fb574a96fb4 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -13,6 +13,7 @@
 #include "base/observer_list.h"
 #include "base/process/process_handle.h"
 #include "base/strings/string16.h"
+#include "base/threading/thread_checker.h"
 #include "base/timer/timer.h"
 #include "build/build_config.h"
 #include "content/child/child_thread.h"
@@ -504,6 +505,11 @@ class CONTENT_EXPORT RenderThreadImpl : public RenderThread,
 
   base::ProcessId renderer_process_id_;
 
+  // TODO(reveman): Allow AllocateGpuMemoryBuffer to be called from
+  // multiple threads. Current allocation mechanism for IOSurface
+  // backed GpuMemoryBuffers prevent this. crbug.com/325045
+  base::ThreadChecker allocate_gpu_memory_buffer_thread_checker_;
+
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };