Explicit initialization of aura::Env for browser shell.

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/command_line.h"
 #include "ui/aura/env_observer.h"
 #include "ui/aura/root_window_host.h"
 #include "ui/aura/window.h"
@@ skipping 21 matching lines @@
 #if defined(USE_X11)
   base::MessagePumpX11::Current()->RemoveObserver(
       &device_list_updater_aurax11_);
 #endif
 
   FOR_EACH_OBSERVER(EnvObserver, observers_, OnWillDestroyEnv());
 
   ui::Compositor::Terminate();
 }
 
+//static
+void Env::CreateInstance() {
+  if (!instance_) {
+    instance_ = new Env;
+    instance_->Init();
+  }
+}
+
 // static
 Env* Env::GetInstance() {
-  if (!instance_) {
-    instance_ = new Env;
-    instance_->Init();
-  }
+  DCHECK(instance_) << "Env::CreateInstance must be called before getting "
+                       "the instance of Env.";
   return instance_;
 }
 
 // static
 void Env::DeleteInstance() {
   delete instance_;
   instance_ = NULL;
 }
 
 void Env::AddObserver(EnvObserver* observer) {
   observers_.AddObserver(observer);
 }
 
 void Env::RemoveObserver(EnvObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID) && \
+    !defined(USE_GTK_MESSAGE_PUMP)
 base::MessageLoop::Dispatcher* Env::GetDispatcher() {
 #if defined(USE_X11)
   return base::MessagePumpX11::Current();
 #else
   return dispatcher_.get();
 #endif
 }
+#endif
 
 void Env::RootWindowActivated(RootWindow* root_window) {
   FOR_EACH_OBSERVER(EnvObserver, observers_,
                     OnRootWindowActivated(root_window));
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // Env, private:
 
 void Env::Init() {
-#if !defined(USE_X11) && !defined(USE_OZONE)
+#if !defined(OS_MACOSX) && !defined(OS_ANDROID) && !defined(USE_X11) && \
+    !defined(USE_OZONE)
   dispatcher_.reset(CreateDispatcher());
 #endif
 #if defined(USE_X11)
   // We can't do this with a root window listener because XI_HierarchyChanged
   // messages don't have a target window.
   base::MessagePumpX11::Current()->AddObserver(
       &device_list_updater_aurax11_);
 #endif
   ui::Compositor::Initialize();
 }
@@ skipping 13 matching lines @@
 
 bool Env::CanAcceptEvent(const ui::Event& event) {
   return true;
 }
 
 ui::EventTarget* Env::GetParentTarget() {
   return NULL;
 }
 
 }  // namespace aura