linux and chromeos: Turn on -Wunused-const-variable.

ash/desktop_background/desktop_background_controller.cc

 // Copyright (c) 2012 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 "ash/desktop_background/desktop_background_controller.h"
 
 #include "ash/ash_switches.h"
 #include "ash/desktop_background/desktop_background_controller_observer.h"
 #include "ash/desktop_background/desktop_background_view.h"
 #include "ash/desktop_background/desktop_background_widget_controller.h"
@@ skipping 25 matching lines @@
 using ash::internal::DesktopBackgroundWidgetController;
 using content::BrowserThread;
 
 namespace ash {
 namespace {
 
 // How long to wait reloading the wallpaper after the max display has
 // changed?
 const int kWallpaperReloadDelayMs = 2000;
 
-const SkColor kTransparentColor = SkColorSetARGB(0x00, 0x00, 0x00, 0x00);
-
 internal::RootWindowLayoutManager* GetRootWindowLayoutManager(
     aura::RootWindow* root_window) {
   return static_cast<internal::RootWindowLayoutManager*>(
       root_window->layout_manager());
 }
 
 }  // namespace
 
 const int kSmallWallpaperMaxWidth = 1366;
 const int kSmallWallpaperMaxHeight = 800;
@@ skipping 405 matching lines @@
         iter->rotation() == gfx::Display::ROTATE_270) {
       size_in_pixel = gfx::Size(size_in_pixel.height(), size_in_pixel.width());
     }
     width = std::max(size_in_pixel.width(), width);
     height = std::max(size_in_pixel.height(), height);
   }
   return gfx::Size(width, height);
 }
 
 }  // namespace ash