Reland " Preload default wallpaper."

ash/desktop_background/desktop_background_controller.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 "ash/desktop_background/desktop_background_controller.h"
 
 #include "ash/desktop_background/desktop_background_view.h"
 #include "ash/desktop_background/desktop_background_widget_controller.h"
 #include "ash/shell.h"
 #include "ash/shell_factory.h"
@@ skipping 133 matching lines @@
            wallpaper_height < root_window_size.height()) &&
           current_wallpaper_->wallpaper_index != -1 &&
           current_wallpaper_->wallpaper_layout != TILE)
         SetDefaultWallpaper(current_wallpaper_->wallpaper_index, true);
     }
   }
 
   InstallComponent(root_window);
 }
 
+void DesktopBackgroundController::CacheDefaultWallpaper(int index) {
+  DCHECK(index >= 0);
+
+  WallpaperResolution resolution = GetAppropriateResolution();
+  scoped_refptr<WallpaperOperation> wallpaper_op =
+      new WallpaperOperation(index, resolution);
+  base::WorkerPool::PostTask(
+      FROM_HERE,
+      base::Bind(&WallpaperOperation::Run, wallpaper_op),
+      true);
+}
+
 void DesktopBackgroundController::SetDefaultWallpaper(int index,
                                                       bool force_reload) {
   // We should not change background when index is invalid. For instance, at
   // login screen or stub_user login.
   if (index == GetInvalidWallpaperIndex()) {
     CreateEmptyWallpaper();
     return;
   } else if (index == GetSolidColorIndex()) {
     SetDesktopBackgroundSolidColorMode(kLoginWallpaperColor);
     return;
   }
 
   if (!force_reload && current_wallpaper_.get() &&
       current_wallpaper_->wallpaper_index == index)
     return;
 
   CancelPendingWallpaperOperation();
 
-  WallpaperResolution resolution = SMALL;
-  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
-  for (Shell::RootWindowList::iterator iter = root_windows.begin();
-       iter != root_windows.end(); ++iter) {
-    gfx::Size root_window_size = (*iter)->GetHostSize();
-    if (root_window_size.width() > kSmallWallpaperMaximalWidth ||
-        root_window_size.height() > kSmallWallpaperMaximalHeight)
-      resolution = LARGE;
-  }
+  WallpaperResolution resolution = GetAppropriateResolution();
 
   wallpaper_op_ = new WallpaperOperation(index, resolution);
   base::WorkerPool::PostTaskAndReply(
       FROM_HERE,
       base::Bind(&WallpaperOperation::Run, wallpaper_op_),
       base::Bind(&DesktopBackgroundController::OnWallpaperLoadCompleted,
                  weak_ptr_factory_.GetWeakPtr(),
                  wallpaper_op_),
       true /* task_is_slow */);
 }
@@ skipping 157 matching lines @@
                         src_container,
                         dst_container);
   }
 }
 
 int DesktopBackgroundController::GetBackgroundContainerId(bool locked) {
   return locked ? internal::kShellWindowId_LockScreenBackgroundContainer :
                   internal::kShellWindowId_DesktopBackgroundContainer;
 }
 
+WallpaperResolution DesktopBackgroundController::GetAppropriateResolution() {
+  WallpaperResolution resolution = SMALL;
+  Shell::RootWindowList root_windows = Shell::GetAllRootWindows();
+  for (Shell::RootWindowList::iterator iter = root_windows.begin();
+       iter != root_windows.end(); ++iter) {
+    gfx::Size root_window_size = (*iter)->GetHostSize();
+    if (root_window_size.width() > kSmallWallpaperMaximalWidth ||
+        root_window_size.height() > kSmallWallpaperMaximalHeight)
+      resolution = LARGE;
+  }
+  return resolution;
+}
+
 }  // namespace ash