Theme suppliers: Avoid all Image copying.

chrome/browser/supervised_user/supervised_user_theme.cc

 // Copyright 2014 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/supervised_user/supervised_user_theme.h"
 
 #include "chrome/browser/themes/theme_properties.h"
 #include "grit/theme_resources.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/image/image.h"
@@ skipping 38 matching lines @@
     case ThemeProperties::COLOR_SUPERVISED_USER_LABEL:
       *color = SK_ColorWHITE;
       return true;
     case ThemeProperties::COLOR_SUPERVISED_USER_LABEL_BACKGROUND:
       *color = kDefaultColorSupervisedUserLabelBackground;
       return true;
   }
   return false;
 }
 
-gfx::Image SupervisedUserTheme::GetImageNamed(int id) {
+const gfx::Image& SupervisedUserTheme::GetImageNamed(int id) {
   if (!HasCustomImage(id))
-    return gfx::Image();
+    return empty_image();
 
   id = MapToSupervisedUserResourceIds(id);
   return ResourceBundle::GetSharedInstance().GetNativeImageNamed(id);
 }
 
 bool SupervisedUserTheme::HasCustomImage(int id) const {
   return id != MapToSupervisedUserResourceIds(id);
 }