Cleanup: Pull some browser keep alive functions into its own file.

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/memory/scoped_ptr.h"
 #include "ui/gfx/native_widget_types.h"
 
+namespace browser_lifetime {
+class ScopedKeepAlive;
+}
+
 // Class to scoped decrement keep alive count.
 class AutoKeepAlive {
  public:
   explicit AutoKeepAlive(gfx::NativeWindow window);
   ~AutoKeepAlive();
 
  private:
-  bool keep_alive_available_;
+  scoped_ptr<browser_lifetime::ScopedKeepAlive> keep_alive_;
 
   DISALLOW_COPY_AND_ASSIGN(AutoKeepAlive);
 };
 
 #endif  // CHROME_BROWSER_UI_VIEWS_AUTO_KEEP_ALIVE_H_