Add MGLEcho

mojo/gles2/gles2_context.h

Index: mojo/gles2/gles2_context.h
diff --git a/mojo/gles2/gles2_context.h b/mojo/gles2/gles2_context.h
index 932a85eb46a40a32ef8081def84ed1075427e27d..52fdaebb811bd61f9e795f130d4bacce5faa97aa 100644
--- a/mojo/gles2/gles2_context.h
+++ b/mojo/gles2/gles2_context.h
@@ -9,6 +9,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "gpu/command_buffer/client/gles2_implementation.h"
 #include "mojo/gles2/command_buffer_client_impl.h"
+#include "mojo/public/c/gpu/MGL/mgl_echo.h"
 #include "mojo/public/c/gpu/MGL/mgl_signal_sync_point.h"
 #include "mojo/public/c/gpu/MGL/mgl_types.h"
 
@@ -38,6 +39,8 @@ class GLES2Context : public CommandBufferDelegate, public MGLContextPrivate {
   }
   gpu::ContextSupport* context_support() const { return implementation_.get(); }
 
+  void Echo(MGLEchoCallback callback, void* closure);
+
   void SignalSyncPoint(uint32_t sync_point,
                        MGLSignalSyncPointCallback callback,
                        void* closure);