Add MGLEcho

mojo/gles2/control_thunks_impl.cc

Index: mojo/gles2/control_thunks_impl.cc
diff --git a/mojo/gles2/control_thunks_impl.cc b/mojo/gles2/control_thunks_impl.cc
index ab0d48c52a6963cc3d4b6ba2c22f9d86cba876fa..0cb679a2c0d448ab2afb4faf3b4b34de3a085819 100644
--- a/mojo/gles2/control_thunks_impl.cc
+++ b/mojo/gles2/control_thunks_impl.cc
@@ -79,6 +79,10 @@ void* ControlThunksImpl::GetGLES2Interface(MGLContext context) {
   return client->interface();
 }
 
+void ControlThunksImpl::Echo(MGLEchoCallback callback, void* closure) {
+  current_context_tls_.Get()->Echo(callback, closure);
+}
+
 void ControlThunksImpl::SignalSyncPoint(
     uint32_t sync_point,
     MGLSignalSyncPointCallback callback,