mus: Make sure WindowCompositorFrameSink is detached correctly.

services/ui/public/cpp/window_compositor_frame_sink.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 "services/ui/public/cpp/window_compositor_frame_sink.h"
 
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_sink_client.h"
@@ skipping 38 matching lines @@
 
   begin_frame_source_ = base::MakeUnique<cc::ExternalBeginFrameSource>(this);
 
   client->SetBeginFrameSource(begin_frame_source_.get());
   return true;
 }
 
 void WindowCompositorFrameSink::DetachFromClient() {
   client_->SetBeginFrameSource(nullptr);
   begin_frame_source_.reset();
+  client_binding_.reset();
   compositor_frame_sink_.reset();
   cc::CompositorFrameSink::DetachFromClient();
 }
 
 void WindowCompositorFrameSink::SubmitCompositorFrame(
     cc::CompositorFrame frame) {
   DCHECK(thread_checker_);
   DCHECK(thread_checker_->CalledOnValidThread());
   if (!compositor_frame_sink_)
     return;
@@ skipping 67 matching lines @@
 WindowCompositorFrameSinkBinding::TakeFrameSinkRequest() {
   return std::move(compositor_frame_sink_request_);
 }
 
 cc::mojom::MojoCompositorFrameSinkClientPtrInfo
 WindowCompositorFrameSinkBinding::TakeFrameSinkClient() {
   return std::move(compositor_frame_sink_client_);
 }
 
 }  // namespace ui