Theme suppliers: Avoid all Image copying.

chrome/browser/ui/libgtk2ui/gtk2_ui.h

 // Copyright (c) 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.
 
 #ifndef CHROME_BROWSER_UI_LIBGTK2UI_GTK2_UI_H_
 #define CHROME_BROWSER_UI_LIBGTK2UI_GTK2_UI_H_
 
 #include <map>
 #include <memory>
 #include <vector>
@@ skipping 58 matching lines @@
   // ui::ShellDialogLinux:
   ui::SelectFileDialog* CreateSelectFileDialog(
       ui::SelectFileDialog::Listener* listener,
       ui::SelectFilePolicy* policy) const override;
 
   // ui::LinuxUI:
   void Initialize() override;
   // TODO(varkha): This should not be necessary once Material Design is on
   // unconditionally.
   void MaterialDesignControllerReady() override;
-  gfx::Image GetThemeImageNamed(int id) const override;
+  const gfx::Image& GetThemeImageNamed(int id) const override;
   bool GetTint(int id, color_utils::HSL* tint) const override;
   bool GetColor(int id, SkColor* color) const override;
   bool HasCustomImage(int id) const override;
   SkColor GetFocusRingColor() const override;
   SkColor GetThumbActiveColor() const override;
   SkColor GetThumbInactiveColor() const override;
   SkColor GetTrackColor() const override;
   SkColor GetActiveSelectionBgColor() const override;
   SkColor GetActiveSelectionFgColor() const override;
   SkColor GetInactiveSelectionBgColor() const override;
@@ skipping 155 matching lines @@
 }  // namespace libgtk2ui
 
 // Access point to the GTK2 desktop system. This should be the only symbol that
 // is exported in the library; everything else should be used through the
 // interface, because eventually this .so will be loaded through dlopen at
 // runtime so our main binary can conditionally load GTK2 or GTK3 or EFL or
 // QT or whatever.
 LIBGTK2UI_EXPORT views::LinuxUI* BuildGtk2UI();
 
 #endif  // CHROME_BROWSER_UI_LIBGTK2UI_GTK2_UI_H_