If customization includes default wallpaper, download and apply it.

ash/desktop_background/desktop_background_controller.h

Index: ash/desktop_background/desktop_background_controller.h
diff --git a/ash/desktop_background/desktop_background_controller.h b/ash/desktop_background/desktop_background_controller.h
index 505f7441792b86584a009f06becf2453195119f0..7938106351e41b0a816b8282fb81a520f24ab2ed 100644
--- a/ash/desktop_background/desktop_background_controller.h
+++ b/ash/desktop_background/desktop_background_controller.h
@@ -23,10 +23,6 @@ namespace aura {
 class Window;
 }
 
-namespace base {
-class CommandLine;
-}
-
 namespace ash {
 
 enum WallpaperLayout {
@@ -83,10 +79,6 @@ class ASH_EXPORT DesktopBackgroundController
     return desktop_background_mode_;
   }
 
-  void set_command_line_for_testing(base::CommandLine* command_line) {
-    command_line_for_testing_ = command_line;
-  }
-
   // Add/Remove observers.
   void AddObserver(DesktopBackgroundControllerObserver* observer);
   void RemoveObserver(DesktopBackgroundControllerObserver* observer);
@@ -104,7 +96,8 @@ class ASH_EXPORT DesktopBackgroundController
   // after loaded. Returns true if the controller started loading the
   // wallpaper and false otherwise (i.e. the appropriate wallpaper was
   // already loading or loaded).
-  bool SetDefaultWallpaper(bool is_guest);
+  bool SetDefaultWallpaper(const base::FilePath& small_resolution_path,
+                           const base::FilePath& large_resolution_path);
 
   // Sets the user selected custom wallpaper. Called when user selected a file
   // from file system or changed the layout of wallpaper.
@@ -135,6 +128,13 @@ class ASH_EXPORT DesktopBackgroundController
   // Overrides DisplayController::Observer:
   virtual void OnDisplayConfigurationChanged() OVERRIDE;
 
+  // Returns true if the specified default wallpaper file is already being
+  // loaded by |wallpaper_loader_| or stored in |current_wallpaper_|.
+  // (i.e. if current wallpaper is "default" and we need to replace the default
+  // wallpaper with another file, we need to initiate SetDefaultWallpaper() )
+  bool DefaultWallpaperFileIsAlreadyLoadingOrLoaded(
+      const base::FilePath& image_file) const;
+
  private:
   friend class DesktopBackgroundControllerTest;
   FRIEND_TEST_ALL_PREFIXES(DesktopBackgroundControllerTest, GetMaxDisplaySize);
@@ -144,6 +144,7 @@ class ASH_EXPORT DesktopBackgroundController
 
   // Returns true if the specified default wallpaper is already being
   // loaded by |wallpaper_loader_| or stored in |current_wallpaper_|.
+  // (i.e. no need to reload if exactly duplicate request received)
   bool DefaultWallpaperIsAlreadyLoadingOrLoaded(
       const base::FilePath& image_file, int image_resource_id) const;
 
@@ -190,9 +191,6 @@ class ASH_EXPORT DesktopBackgroundController
   // maximum width of all displays, and the maximum height of all displays.
   static gfx::Size GetMaxDisplaySizeInNative();
 
-  // If non-NULL, used in place of the real command line.
-  base::CommandLine* command_line_for_testing_;
-
   // Can change at runtime.
   bool locked_;