Add ScopedKeepAlive to c/b/lifetime

chrome/browser/ui/views/auto_keep_alive.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 CHROME_BROWSER_UI_VIEWS_AUTO_KEEP_ALIVE_H_
 #define CHROME_BROWSER_UI_VIEWS_AUTO_KEEP_ALIVE_H_
 
-#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
 #include "ui/gfx/native_widget_types.h"
 
-// Class to scoped decrement keep alive count.
-class AutoKeepAlive {
- public:
-  explicit AutoKeepAlive(gfx::NativeWindow window);
-  ~AutoKeepAlive();
+class ScopedKeepAlive;
 
- private:
-  bool keep_alive_available_;
-
-  DISALLOW_COPY_AND_ASSIGN(AutoKeepAlive);
-};
+// Returns a keep alive object for the caller to take ownership of.
+// On Ash environments, will return a null pointer.
+scoped_ptr<ScopedKeepAlive> AutoKeepAlive(gfx::NativeWindow window);
 
 #endif  // CHROME_BROWSER_UI_VIEWS_AUTO_KEEP_ALIVE_H_