ozone: Initialize a subsystem only if necessary.

ui/aura/env.cc

 // Copyright (c) 2012 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/env.h"
 
 #include "base/lazy_instance.h"
 #include "base/threading/thread_local.h"
 #include "ui/aura/env_observer.h"
 #include "ui/aura/input_state_lookup.h"
 #include "ui/events/event_target_iterator.h"
 #include "ui/events/platform/platform_event_source.h"
 
+#if defined(USE_OZONE)
+#include "ui/ozone/ozone_platform.h"
+#endif
+
 namespace aura {
 
 namespace {
 
 // Env is thread local so that aura may be used on multiple threads.
 base::LazyInstance<base::ThreadLocalPointer<Env> >::Leaky lazy_tls_ptr =
     LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
 
@@ skipping 43 matching lines @@
   lazy_tls_ptr.Pointer()->Set(this);
 }
 
 Env::~Env() {
   FOR_EACH_OBSERVER(EnvObserver, observers_, OnWillDestroyEnv());
   DCHECK_EQ(this, lazy_tls_ptr.Pointer()->Get());
   lazy_tls_ptr.Pointer()->Set(NULL);
 }
 
 void Env::Init(bool create_event_source) {
+#if defined(USE_OZONE)
+  // The ozone platform can provide its own event source. So initialize the
+  // platform before creating the default event source.
+  ui::OzonePlatform::InitializeForUI();
+#endif
   if (create_event_source && !ui::PlatformEventSource::GetInstance())
     event_source_ = ui::PlatformEventSource::CreateDefault();
 }
 
 void Env::NotifyWindowInitialized(Window* window) {
   FOR_EACH_OBSERVER(EnvObserver, observers_, OnWindowInitialized(window));
 }
 
 void Env::NotifyHostInitialized(WindowTreeHost* host) {
   FOR_EACH_OBSERVER(EnvObserver, observers_, OnHostInitialized(host));
@@ skipping 17 matching lines @@
 scoped_ptr<ui::EventTargetIterator> Env::GetChildIterator() const {
   return scoped_ptr<ui::EventTargetIterator>();
 }
 
 ui::EventTargeter* Env::GetEventTargeter() {
   NOTREACHED();
   return NULL;
 }
 
 }  // namespace aura