Theme suppliers: Avoid all Image copying.

chrome/browser/themes/theme_service_aurax11.cc

Index: chrome/browser/themes/theme_service_aurax11.cc
diff --git a/chrome/browser/themes/theme_service_aurax11.cc b/chrome/browser/themes/theme_service_aurax11.cc
index 71a573ab303036f13f63031db536f328bff3cb82..0e6897123cb2e4492332a0dc6a7c572c081b0856 100644
--- a/chrome/browser/themes/theme_service_aurax11.cc
+++ b/chrome/browser/themes/theme_service_aurax11.cc
@@ -25,7 +25,7 @@ class SystemThemeX11 : public CustomThemeSupplier {
   void StopUsingTheme() override;
   bool GetTint(int id, color_utils::HSL* hsl) const override;
   bool GetColor(int id, SkColor* color) const override;
-  gfx::Image GetImageNamed(int id) override;
+  const gfx::Image& GetImageNamed(int id) override;
   bool HasCustomImage(int id) const override;
 
  private:
@@ -64,8 +64,8 @@ bool SystemThemeX11::GetColor(int id, SkColor* color) const {
   return linux_ui_ && linux_ui_->GetColor(id, color);
 }
 
-gfx::Image SystemThemeX11::GetImageNamed(int id) {
-  return linux_ui_ ? linux_ui_->GetThemeImageNamed(id) : gfx::Image();
+const gfx::Image& SystemThemeX11::GetImageNamed(int id) {
+  return linux_ui_ ? linux_ui_->GetThemeImageNamed(id) : empty_image();
 }
 
 bool SystemThemeX11::HasCustomImage(int id) const {