Invalidate all wallpaper cache if display configuration changed

ash/test/test_user_wallpaper_delegate.cc

 // 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.
 
 #include "ash/test/test_user_wallpaper_delegate.h"
 
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/shell.h"
 
 namespace ash {
 namespace test {
 
 TestUserWallpaperDelegate::TestUserWallpaperDelegate()
     : update_wallpaper_count_(0) {}
 
 TestUserWallpaperDelegate::~TestUserWallpaperDelegate() {}
 
-void TestUserWallpaperDelegate::UpdateWallpaper() {
-  DefaultUserWallpaperDelegate::UpdateWallpaper();
+void TestUserWallpaperDelegate::UpdateWallpaper(bool clear_cache) {
+  DefaultUserWallpaperDelegate::UpdateWallpaper(clear_cache);
   if (!custom_wallpaper_.isNull()) {
     Shell::GetInstance()->desktop_background_controller()->SetCustomWallpaper(
         custom_wallpaper_, WALLPAPER_LAYOUT_STRETCH);
   }
   update_wallpaper_count_++;
 }
 
 int TestUserWallpaperDelegate::GetUpdateWallpaperCountAndReset() {
   int count = update_wallpaper_count_;
   update_wallpaper_count_ = 0;
   return count;
 }
 
 }  // namespace test
 }  // namespace ash