Enable user change background image in settings page in Aura build.

chrome/browser/chromeos/chrome_browser_main_chromeos.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 CHROME_BROWSER_CHROMEOS_CHROME_BROWSER_MAIN_CHROMEOS_H_
 #define CHROME_BROWSER_CHROMEOS_CHROME_BROWSER_MAIN_CHROMEOS_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "chrome/browser/chrome_browser_main_linux.h"
 
 namespace chromeos {
 class BrightnessObserver;
 class ResumeObserver;
 class ScreenLockObserver;
 class SessionManagerObserver;
 
+#if defined(USE_ASH)
+class DesktopBackgroundObserver;
+#endif
+
 #if defined(USE_AURA)
 class InitialBrowserWindowObserver;
 class PowerButtonObserver;
 class VideoPropertyWriter;
 #endif
 }  // namespace chromeos
 
 class ChromeBrowserMainPartsChromeos : public ChromeBrowserMainPartsLinux {
  public:
   explicit ChromeBrowserMainPartsChromeos(
@@ skipping 13 matching lines @@
   virtual void PostBrowserStart() OVERRIDE;
 
   virtual void PostMainMessageLoopRun() OVERRIDE;
 
  private:
   scoped_ptr<chromeos::BrightnessObserver> brightness_observer_;
   scoped_ptr<chromeos::ResumeObserver> resume_observer_;
   scoped_ptr<chromeos::ScreenLockObserver> screen_lock_observer_;
   scoped_ptr<chromeos::SessionManagerObserver> session_manager_observer_;
 
+#if defined(USE_ASH)
+  scoped_ptr<chromeos::DesktopBackgroundObserver> desktop_background_observer_;
+#endif
+
 #if defined(USE_AURA)
   scoped_ptr<chromeos::InitialBrowserWindowObserver>
       initial_browser_window_observer_;
   scoped_ptr<chromeos::PowerButtonObserver> power_button_observer_;
   scoped_ptr<chromeos::VideoPropertyWriter> video_property_writer_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ChromeBrowserMainPartsChromeos);
 };
 
 #endif  // CHROME_BROWSER_CHROMEOS_CHROME_BROWSER_MAIN_CHROMEOS_H_