(not for commit) Simplified multi-threaded Ganesh with lock on Flush only.

gpu/command_buffer/client/gles2_interface.h

Index: gpu/command_buffer/client/gles2_interface.h
diff --git a/gpu/command_buffer/client/gles2_interface.h b/gpu/command_buffer/client/gles2_interface.h
index 0b0bc514f2489822582482a66fa8806237cd5e12..61a1ca41217b5c68436925a1b9444fe97ab80716 100644
--- a/gpu/command_buffer/client/gles2_interface.h
+++ b/gpu/command_buffer/client/gles2_interface.h
@@ -24,6 +24,9 @@ class GLES2Interface {
   // it means we can easily edit the non-auto generated parts right here in
   // this file instead of having to edit some template or the code generator.
   #include "gpu/command_buffer/client/gles2_interface_autogen.h"
+
+  virtual void SetSafeFlushPoint(){};
+  virtual void SafeFlush(){};
 };
 
 }  // namespace gles2