aura: Require explicit ownership of the Env instance.

ui/aura/env.h

 // 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.
 
 #ifndef UI_AURA_ENV_H_
 #define UI_AURA_ENV_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "base/observer_list.h"
 #include "base/supports_user_data.h"
@@ skipping 13 matching lines @@
 }
 
 class EnvObserver;
 class InputStateLookup;
 class Window;
 class WindowTreeHost;
 
 // A singleton object that tracks general state within Aura.
 class AURA_EXPORT Env : public ui::EventTarget, public base::SupportsUserData {
  public:
-  // Creates the single Env instance (if it hasn't been created yet). If
-  // |create_event_source| is true a PlatformEventSource is created.
-  // TODO(sky): nuke |create_event_source|. Only necessary while mojo's
-  // nativeviewportservice lives in the same process as the viewmanager.
-  static void CreateInstance(bool create_event_source);
+  ~Env() override;
+
+  static scoped_ptr<Env> CreateInstance();
   static Env* GetInstance();
   static Env* GetInstanceDontCreate();
-  static void DeleteInstance();
 
   void AddObserver(EnvObserver* observer);
   void RemoveObserver(EnvObserver* observer);
 
   int mouse_button_flags() const { return mouse_button_flags_; }
   void set_mouse_button_flags(int mouse_button_flags) {
     mouse_button_flags_ = mouse_button_flags;
   }
   // Returns true if a mouse button is down. This may query the native OS,
   // otherwise it uses |mouse_button_flags_|.
@@ skipping 14 matching lines @@
     context_factory_ = context_factory;
   }
   ui::ContextFactory* context_factory() { return context_factory_; }
 
  private:
   friend class test::EnvTestHelper;
   friend class Window;
   friend class WindowTreeHost;
 
   Env();
-  ~Env() override;
 
-  // See description of CreateInstance() for deatils of |create_event_source|.
-  void Init(bool create_event_source);
+  void Init();
 
   // Called by the Window when it is initialized. Notifies observers.
   void NotifyWindowInitialized(Window* window);
 
   // Called by the WindowTreeHost when it is initialized. Notifies observers.
   void NotifyHostInitialized(WindowTreeHost* host);
 
   // Invoked by WindowTreeHost when it is activated. Notifies observers.
   void NotifyHostActivated(WindowTreeHost* host);
 
@@ skipping 14 matching lines @@
   scoped_ptr<ui::PlatformEventSource> event_source_;
 
   ui::ContextFactory* context_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Env);
 };
 
 }  // namespace aura
 
 #endif  // UI_AURA_ENV_H_