Speed up custom wallpaper switching time and wallpaper manager code refactor

chrome/browser/chromeos/chrome_browser_main_chromeos.cc

 // 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.
 
 #include "chrome/browser/chromeos/chrome_browser_main_chromeos.h"
 
 #include <string>
 #include <vector>
 
 #include "base/bind.h"
@@ skipping 266 matching lines @@
   ChromeBrowserMainPartsLinux::PreMainMessageLoopStart();
 }
 
 void ChromeBrowserMainPartsChromeos::PostMainMessageLoopStart() {
   MessageLoopForUI* message_loop = MessageLoopForUI::current();
   message_loop->AddObserver(g_message_loop_observer.Pointer());
 
   // Initialize DBusThreadManager for the browser. This must be done after
   // the main message loop is started, as it uses the message loop.
   chromeos::DBusThreadManager::Initialize();
-  // Add PowerManagerClient observer for WallpaperManager. WallpaperManager
-  // is initialized before DBusThreadManager.
-  chromeos::WallpaperManager::Get()->AddPowerManagerClientObserver();
+  // Add observers for WallpaperManager. WallpaperManager is initialized before
+  // DBusThreadManager.
+  chromeos::WallpaperManager::Get()->AddObservers();
 
   chromeos::CrosDBusService::Initialize();
 
   // Initialize the session manager observer so that we'll take actions
   // per signals sent from the session manager.
   session_manager_observer_.reset(new chromeos::SessionManagerObserver);
 
   chromeos::disks::DiskMountManager::Initialize();
   cryptohome::AsyncMethodCaller::Initialize();
 
@@ skipping 281 matching lines @@
       LOG(WARNING) << "low_mem: Part of '100MB' experiment";
       chromeos::LowMemoryObserver::SetLowMemoryMargin(100);
     } else if (trial->group() == margin_200mb) {
       LOG(WARNING) << "low_mem: Part of '200MB' experiment";
       chromeos::LowMemoryObserver::SetLowMemoryMargin(200);
     } else {
       LOG(WARNING) << "low_mem: Part of 'default' experiment";
     }
   }
 }