mus: Embedder can request and observe BeginFrame for embedded client.

ui/aura/mus/window_tree_client.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 "ui/aura/mus/window_tree_client.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 880 matching lines @@
   if (transport_value)
     transport_value_mojo.emplace(std::move(*transport_value));
 
   const uint32_t change_id =
       ScheduleInFlightChange(base::MakeUnique<InFlightPropertyChange>(
           window, transport_name, std::move(data_mus->transport_value)));
   tree_->SetWindowProperty(change_id, window->server_id(), transport_name,
                            transport_value_mojo);
 }
 
+void WindowTreeClient::RequestBeginFrames(
+    WindowMus* window,
+    cc::mojom::FrameSinkObserverPtr observer) {
+  tree_->RequestBeginFrames(window->server_id(), std::move(observer));
+}
+
 void WindowTreeClient::OnWmMoveLoopCompleted(uint32_t change_id,
                                              bool completed) {
   if (window_manager_client_)
     window_manager_client_->WmResponse(change_id, completed);
 
   if (change_id == current_wm_move_loop_change_) {
     current_wm_move_loop_change_ = 0;
     current_wm_move_loop_window_id_ = 0;
   }
 }
@@ skipping 1165 matching lines @@
 }
 
 void WindowTreeClient::OnCompositingLockStateChanged(
     ui::Compositor* compositor) {}
 
 void WindowTreeClient::OnCompositingShuttingDown(ui::Compositor* compositor) {
   compositor->RemoveObserver(this);
 }
 
 }  // namespace aura