Theme suppliers: Avoid all Image copying.

chrome/browser/themes/custom_theme_supplier.cc

Index: chrome/browser/themes/custom_theme_supplier.cc
diff --git a/chrome/browser/themes/custom_theme_supplier.cc b/chrome/browser/themes/custom_theme_supplier.cc
index 657f218341f5e91c0059c69b3e99d78a1c8852cc..5c71159be31d56ce86758ae84d6ee2584195a327 100644
--- a/chrome/browser/themes/custom_theme_supplier.cc
+++ b/chrome/browser/themes/custom_theme_supplier.cc
@@ -6,7 +6,6 @@
 
 #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) {}
@@ -29,8 +28,8 @@ 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(