Split ExtensionSystem interface from ExtensionSystemImpl implementation, part 1.

apps/shell/shell_extension_system.h

 // Copyright 2013 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 APPS_SHELL_SHELL_EXTENSION_SYSTEM_H_
 #define APPS_SHELL_SHELL_EXTENSION_SYSTEM_H_
 
 #include "base/compiler_specific.h"
-#include "chrome/browser/extensions/extension_system.h"
+#include "extensions/browser/extension_system.h"
 #include "extensions/common/one_shot_event.h"
 
 namespace base {
 class FilePath;
 }
 
 namespace content {
 class BrowserContext;
 }
 
@@ skipping 55 matching lines @@
 
   // Signaled when the extension system has completed its startup tasks.
   OneShotEvent ready_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellExtensionSystem);
 };
 
 }  // namespace extensions
 
 #endif  // APPS_SHELL_SHELL_EXTENSION_SYSTEM_H_