Implement user selected wallpaper feature.

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 b31a21464120ef1ecdff7e6f8e64f0ecb3c23329..a531001f57bc6ea46f4680bdd34db04bb71517b6 100644
--- a/ash/desktop_background/desktop_background_controller.h
+++ b/ash/desktop_background/desktop_background_controller.h
@@ -22,7 +22,7 @@ class UserWallpaperDelegate {
   // Gets the index of user selected wallpaper.
   virtual const int GetUserWallpaperIndex() = 0;
 
-  // Open the set wallpaper page in the browser.
+  // Opens the set wallpaper page in the browser.
   virtual void OpenSetWallpaperPage() = 0;
 
   // Returns true if user can open set wallpaper page. Only guest user returns
@@ -30,8 +30,8 @@ class UserWallpaperDelegate {
   virtual bool CanOpenSetWallpaperPage() = 0;
 };
 
-// A class to listen for login and desktop background change events and set the
-// corresponding default wallpaper in Aura shell.
+// Loads selected desktop wallpaper from file system asynchronously and updates
+// background layer if loaded successfully.
 class ASH_EXPORT DesktopBackgroundController {
  public:
   enum BackgroundMode {
@@ -42,39 +42,44 @@ class ASH_EXPORT DesktopBackgroundController {
   DesktopBackgroundController();
   virtual ~DesktopBackgroundController();
 
-  // Get the desktop background mode.
+  // Gets the desktop background mode.
   BackgroundMode desktop_background_mode() const {
     return desktop_background_mode_;
   }
 
-  // Load default wallpaper at |index| asynchronously and set to current
+  // Loads default wallpaper at |index| asynchronously and sets to current
   // wallpaper after loaded.
   void SetDefaultWallpaper(int index);
 
-  // Cancel the current wallpaper loading operation.
+  // Sets the user selected custom wallpaper. Called when user selected a file
+  // from file system or changed the layout of wallpaper.
+  void SetCustomWallpaper(const SkBitmap& wallpaper, WallpaperLayout layout);
+
+  // Cancels the current wallpaper loading operation.
   void CancelPendingWallpaperOperation();
 
-  // Load logged in user wallpaper asynchronously and set to current wallpaper
+  // Loads logged in user wallpaper asynchronously and sets to current wallpaper
   // after loaded.
   void SetLoggedInUserWallpaper();
 
-  // Sets the desktop background to solid color mode and create a solid color
+  // Sets the desktop background to solid color mode and creates a solid color
   // layout.
   void SetDesktopBackgroundSolidColorMode();
 
  private:
-  // An operation to asynchronously load wallpaper.
+  // An operation to asynchronously loads wallpaper.
   class WallpaperOperation;
 
-  // Sets the desktop background to image mode and create a new background
-  // widget with user selected wallpaper or default wallpaper. Delete the old
+  // Sets the desktop background to image mode and creates a new background
+  // widget with user selected wallpaper or default wallpaper. Deletes the old
   // widget if any.
   void SetDesktopBackgroundImageMode(scoped_refptr<WallpaperOperation> wo);
 
-  // Default wallpapper loaded, set the background mode to image mode.
+  // Creates a new background widget and sets the background mode to image mode.
+  // Called after wallpaper loaded successfully.
   void OnWallpaperLoadCompleted(scoped_refptr<WallpaperOperation> wo);
 
-  // Create an empty wallpaper. Some tests require a wallpaper widget is ready
+  // Creates an empty wallpaper. Some tests require a wallpaper widget is ready
   // when running. However, the wallpaper widgets are now created asynchronously
   // . If loading a real wallpaper, there are cases that these tests crash
   // because the required widget is not ready. This function synchronously