Supprot V2 app: step1

athena/env/public/athena_env.h

 // Copyright 2014 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 ATHENA_ENV_PUBLIC_ATHENA_ENV_H_
 #define ATHENA_ENV_PUBLIC_ATHENA_ENV_H_
 
 #include "athena/athena_export.h"
+#include "base/callback_forward.h"
+
+namespace aura {
+class WindowTreeHost;
+}
 
 namespace gfx {
 class Insets;
 }
 
-namespace aura {
-class WindowTreeHost;
-}
-
 namespace athena {
 
 // AthenaEnv creates/shuts down the environment necessary to
 // start Athena shell.
 class ATHENA_EXPORT AthenaEnv {
  public:
   static void Create();
   static AthenaEnv* Get();
   static void Shutdown();
 
   virtual ~AthenaEnv() {}
 
   // Returns the single WindowTreeHost for the primary display.
   virtual aura::WindowTreeHost* GetHost() = 0;
 
   // Sets the insets for the primary displays's work area.
   virtual void SetDisplayWorkAreaInsets(const gfx::Insets& insets) = 0;
+
+  // Adds the callback called when the athena is about to exit.
+  virtual void AddTerminatingCallback(const base::Closure& closure) = 0;
+  virtual void RemoveTerminatingCallback(const base::Closure& closure) = 0;
+
+  // Called when the athena is about to exist.
+  virtual void OnTerminating() = 0;
 };
 
 }  // namespace athena
 
 #endif  // ATHENA_ENV_PUBLIC_ATHENA_ENV_H_