Theme suppliers: Avoid all Image copying.

chrome/browser/themes/custom_theme_supplier.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 "chrome/browser/themes/custom_theme_supplier.h"
 
 #include "base/memory/ref_counted_memory.h"
 #include "ui/gfx/color_utils.h"
-#include "ui/gfx/image/image.h"
 
 CustomThemeSupplier::CustomThemeSupplier(ThemeType theme_type)
     : theme_type_(theme_type) {}
 
 CustomThemeSupplier::~CustomThemeSupplier() {}
 
 void CustomThemeSupplier::StartUsingTheme() {}
 
 void CustomThemeSupplier::StopUsingTheme() {}
 
 bool CustomThemeSupplier::GetTint(int id, color_utils::HSL* hsl) const {
   return false;
 }
 
 bool CustomThemeSupplier::GetColor(int id, SkColor* color) const {
   return false;
 }
 
 bool CustomThemeSupplier::GetDisplayProperty(int id, int* result) const {
   return false;
 }
 
-gfx::Image CustomThemeSupplier::GetImageNamed(int id) {
-  return gfx::Image();
+const gfx::Image& CustomThemeSupplier::GetImageNamed(int id) {
+  return empty_image();
 }
 
 base::RefCountedMemory* CustomThemeSupplier::GetRawData(
     int idr_id,
     ui::ScaleFactor scale_factor) const {
   return NULL;
 }
 
 bool CustomThemeSupplier::HasCustomImage(int id) const {
   return false;
 }