ozone: Initialize a subsystem only if necessary.

ui/aura/window_tree_host_ozone.cc

 // Copyright 2013 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/window_tree_host_ozone.h"
 
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/base/cursor/ozone/cursor_factory_ozone.h"
 #include "ui/events/ozone/event_factory_ozone.h"
 #include "ui/events/platform/platform_event_source.h"
 #include "ui/gfx/ozone/surface_factory_ozone.h"
-#include "ui/ozone/ozone_platform.h"
 
 namespace aura {
 
 WindowTreeHostOzone::WindowTreeHostOzone(const gfx::Rect& bounds)
     : widget_(0),
       bounds_(bounds) {
-  ui::OzonePlatform::Initialize();
-
   // EventFactoryOzone creates converters that obtain input events from the
   // underlying input system and dispatch them as |ui::Event| instances into
   // Aura.
   ui::EventFactoryOzone::GetInstance()->StartProcessingEvents();
 
   gfx::SurfaceFactoryOzone* surface_factory =
       gfx::SurfaceFactoryOzone::GetInstance();
   widget_ = surface_factory->GetAcceleratedWidget();
 
   ui::PlatformEventSource::GetInstance()->AddPlatformEventDispatcher(this);
@@ skipping 86 matching lines @@
   return new WindowTreeHostOzone(bounds);
 }
 
 // static
 gfx::Size WindowTreeHost::GetNativeScreenSize() {
   NOTIMPLEMENTED();
   return gfx::Size();
 }
 
 }  // namespace aura