Theme suppliers: Avoid all Image copying.

chrome/browser/themes/theme_service_aurax11.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/theme_service_aurax11.h"
 
 #include "base/bind.h"
 #include "base/macros.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/themes/custom_theme_supplier.h"
 #include "chrome/common/pref_names.h"
 #include "components/prefs/pref_service.h"
 #include "ui/gfx/image/image.h"
 #include "ui/native_theme/native_theme_aura.h"
 #include "ui/views/linux_ui/linux_ui.h"
 
 namespace {
 
 class SystemThemeX11 : public CustomThemeSupplier {
  public:
   explicit SystemThemeX11(PrefService* pref_service);
 
   // Overridden from CustomThemeSupplier:
   void StartUsingTheme() override;
   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:
   ~SystemThemeX11() override;
 
   // These pointers are not owned by us.
   views::LinuxUI* const linux_ui_;
   PrefService* const pref_service_;
 
   DISALLOW_COPY_AND_ASSIGN(SystemThemeX11);
@@ skipping 18 matching lines @@
 }
 
 bool SystemThemeX11::GetTint(int id, color_utils::HSL* hsl) const {
   return linux_ui_ && linux_ui_->GetTint(id, hsl);
 }
 
 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 {
   return linux_ui_ && linux_ui_->HasCustomImage(id);
 }
 
 SystemThemeX11::~SystemThemeX11() {}
 
 }  // namespace
 
@@ skipping 15 matching lines @@
 
 bool ThemeServiceAuraX11::UsingDefaultTheme() const {
   return ThemeService::UsingDefaultTheme() && !UsingSystemTheme();
 }
 
 bool ThemeServiceAuraX11::UsingSystemTheme() const {
   const CustomThemeSupplier* theme_supplier = get_theme_supplier();
   return theme_supplier &&
          theme_supplier->get_theme_type() == CustomThemeSupplier::NATIVE_X11;
 }