Speed up custom wallpaper switching time and wallpaper manager code refactor

chrome/browser/chromeos/login/user.h

Index: chrome/browser/chromeos/login/user.h
diff --git a/chrome/browser/chromeos/login/user.h b/chrome/browser/chromeos/login/user.h
index 48d0f6e34d75d6ec0486357acc1b9b76769c6c8e..b6e4d1de7bbd33a07eea74a8a2568087505a3eda 100644
--- a/chrome/browser/chromeos/login/user.h
+++ b/chrome/browser/chromeos/login/user.h
@@ -86,9 +86,6 @@ class User {
   // image has a URL, for other images empty URL is returned.
   GURL image_url() const { return user_image_.url(); }
 
-  // The thumbnail of user custom wallpaper.
-  const SkBitmap& wallpaper_thumbnail() const { return wallpaper_thumbnail_; }
-
   // True if user image is a stub (while real image is being loaded from file).
   bool image_is_stub() const { return image_is_stub_; }
 
@@ -143,7 +140,6 @@ class User {
   std::string display_email_;
   UserImage user_image_;
   OAuthTokenStatus oauth_token_status_;
-  SkBitmap wallpaper_thumbnail_;
 
   // Either index of a default image for the user, |kExternalImageIndex| or
   // |kProfileImageIndex|.