Singletons changes necessary to run the UI Service inside the browser's process.

services/ui/gpu/gpu_main.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/gpu/gpu_main.h"
 
 #include "base/command_line.h"
 #include "base/memory/ptr_util.h"
 #include "base/message_loop/message_loop.h"
 #include "base/power_monitor/power_monitor_device_source.h"
@@ skipping 32 matching lines @@
 }
 #endif  // defined(OS_MACOSX)
 
 }  // namespace
 
 namespace ui {
 
 GpuMain::GpuMain(mojom::GpuMainRequest request)
     : gpu_thread_("GpuThread"),
       io_thread_("GpuIOThread"),
-      power_monitor_(base::MakeUnique<base::PowerMonitorDeviceSource>()),
       binding_(this) {
+  // TODO: crbug.com/609317: Remove this when Mus Window Server and GPU are
+  // split into separate processes. Until then this is necessary to be able to
+  // run Mushrome (chrome --mus) with Mus running in the browser process.
+  if (!base::PowerMonitor::Get()) {
+    power_monitor_ = base::MakeUnique<base::PowerMonitor>(
+        base::MakeUnique<base::PowerMonitorDeviceSource>());
+  }
+
   base::Thread::Options thread_options;
 
 #if defined(OS_WIN)
   thread_options.message_loop_type = base::MessageLoop::TYPE_DEFAULT;
 #elif defined(USE_X11)
   thread_options.message_pump_factory = base::Bind(&CreateMessagePumpX11);
 #elif defined(USE_OZONE)
   // The MessageLoop type required depends on the Ozone platform selected at
   // runtime.
   thread_options.message_loop_type =
@@ skipping 155 matching lines @@
   // TODO(sad): https://crbug.com/645602
 }
 
 bool GpuMain::EnsureSandboxInitialized(
     gpu::GpuWatchdogThread* watchdog_thread) {
   // TODO(sad): https://crbug.com/645602
   return true;
 }
 
 }  // namespace ui