Plumb GpuSwapBuffers completion from Mus GPU thread to WS thread

components/mus/surfaces/surfaces_context_provider.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/mus/surfaces/surfaces_context_provider.h"
 
 #include <stddef.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 96 matching lines @@
 void SurfacesContextProvider::UpdateVSyncParameters(int64_t timebase,
                                                     int64_t interval) {
   if (delegate_)
     delegate_->OnVSyncParametersUpdated(timebase, interval);
 }
 
 void SurfacesContextProvider::DidLoseContext() {
   lost_context_callback_.Run();
 }
 
+void SurfacesContextProvider::GpuCompletedSwapBuffers(gfx::SwapResult result) {
+  if (!swap_buffers_completion_callback_.is_null()) {
+    swap_buffers_completion_callback_.Run(result);
+  }
+}
+
+void SurfacesContextProvider::SetSwapBuffersCompletionCallback(
+    gfx::GLSurface::SwapCompletionCallback callback) {
+  swap_buffers_completion_callback_ = callback;
+}
+
 }  // namespace mus