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::MessagePumpAuraX11::Current()->RemoveObserver(
       &device_list_updater_aurax11_);
 #endif
 
   FOR_EACH_OBSERVER(EnvObserver, observers_, OnWillDestroyEnv());
 
   ui::Compositor::Terminate();
 }
 
+//static
+void Env::CreateInstance() {
+  if (!instance_) {

[dnicoara, 2013/09/10 19:15:00]

I would have liked to have this as a check and only allow calls to  this
function only when |instance_| hasn't been created unfortunately call ordering
in tests (see comment in ash_test_helper.cc) doesn't allow it. This would also
depend on moving the aura::Env::CreateInstance call in aura::RootWindow to
content::MinimalShell, though I think we don't want to do that since we want
creation as close as possible to first use.

+    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) {
@@ skipping 50 matching lines @@
 
 bool Env::CanAcceptEvent(const ui::Event& event) {
   return true;
 }
 
 ui::EventTarget* Env::GetParentTarget() {
   return NULL;
 }
 
 }  // namespace aura