Add MGLEcho

gpu/command_buffer/client/gles2_implementation.cc

Index: gpu/command_buffer/client/gles2_implementation.cc
diff --git a/gpu/command_buffer/client/gles2_implementation.cc b/gpu/command_buffer/client/gles2_implementation.cc
index cc3aaf47e9686284707731c9e6a1fb6724d434a3..077ab451ae1f9e488445e9ddb3a92f7a7b3c9fc3 100644
--- a/gpu/command_buffer/client/gles2_implementation.cc
+++ b/gpu/command_buffer/client/gles2_implementation.cc
@@ -287,6 +287,12 @@ void GLES2Implementation::RunIfContextNotLost(const base::Closure& callback) {
     callback.Run();
 }
 
+void GLES2Implementation::Echo(const base::Closure& callback) {
+  ShallowFlushCHROMIUM();
+  gpu_control_->Echo(base::Bind(&GLES2Implementation::RunIfContextNotLost,
+                                weak_ptr_factory_.GetWeakPtr(), callback));
+}
+
 void GLES2Implementation::SignalSyncPoint(uint32 sync_point,
                                           const base::Closure& callback) {
   gpu_control_->SignalSyncPoint(