services/ui: Have an explicit lifetime/ownership of ui::GpuService.

services/ui/demo/mus_demo.cc

 // Copyright 2016 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/demo/mus_demo.h"
 
 #include "base/time/time.h"
 #include "services/shell/public/cpp/connector.h"
 #include "services/ui/common/gpu_service.h"
 #include "services/ui/public/cpp/bitmap_uploader.h"
@@ skipping 47 matching lines @@
 
 }  // namespace
 
 MusDemo::MusDemo() {}
 
 MusDemo::~MusDemo() {
   delete window_tree_client_;
 }
 
 void MusDemo::OnStart(const shell::Identity& identity) {
-  GpuService::Initialize(connector());
+  gpu_service_ = GpuService::Initialize(connector());
   window_tree_client_ = new WindowTreeClient(this, this, nullptr);
   window_tree_client_->ConnectAsWindowManager(connector());
 }
 
 bool MusDemo::OnConnect(shell::Connection* connection) {
   return true;
 }
 
 void MusDemo::OnEmbed(Window* window) {
   // Not called for the WindowManager.
@@ skipping 94 matching lines @@
       new std::vector<unsigned char>(addr, addr + bytes));
   bitmap_.unlockPixels();
 
   // Send frame to MUS via BitmapUploader.
   uploader_->SetBitmap(bounds.width(), bounds.height(), std::move(data),
                        ui::BitmapUploader::BGRA);
 }
 
 }  // namespace demo
 }  // namespace ui