Enable user change background image in settings page in Aura build.

ash/shell.h

Index: ash/shell.h
diff --git a/ash/shell.h b/ash/shell.h
index e6af0db939fc28b2e00525c0cf7048cd2e9e680f..00ee51254253af120a73a9e686836b83a89d9de8 100644
--- a/ash/shell.h
+++ b/ash/shell.h
@@ -19,6 +19,7 @@
 #include "ui/gfx/insets.h"
 
 class CommandLine;
+class SkBitmap;
 
 namespace aura {
 class EventFilter;
@@ -42,6 +43,7 @@ namespace ash {
 class AcceleratorController;
 class AudioController;
 class BrightnessController;
+class DesktopBackgroundController;
 class Launcher;
 class NestedDispatcherController;
 class NetworkController;
@@ -81,11 +83,6 @@ class WorkspaceController;
 // takes ownership of the Shell.
 class ASH_EXPORT Shell {
  public:
-  enum BackgroundMode {
-    BACKGROUND_IMAGE,
-    BACKGROUND_SOLID_COLOR
-  };
-
   enum Direction {
     FORWARD,
     BACKWARD
@@ -121,8 +118,8 @@ class ASH_EXPORT Shell {
   // Get the singleton RootWindow used by the Shell.
   static aura::RootWindow* GetRootWindow();
 
-  BackgroundMode desktop_background_mode() const {
-    return desktop_background_mode_;
+  internal::RootWindowLayoutManager* root_window_layout() const {
+    return root_window_layout_;
   }
 
   aura::Window* GetContainer(int container_id);
@@ -139,9 +136,6 @@ class ASH_EXPORT Shell {
   // Toggles app list.
   void ToggleAppList();
 
-  // Sets the desktop background mode.
-  void SetDesktopBackgroundMode(BackgroundMode mode);
-
   // Returns true if the screen is locked.
   bool IsScreenLocked() const;
 
@@ -178,6 +172,9 @@ class ASH_EXPORT Shell {
   internal::PartialScreenshotEventFilter* partial_screenshot_filter() {
     return partial_screenshot_filter_.get();
   }
+  DesktopBackgroundController* desktop_background_controller() {
+    return desktop_background_controller_.get();
+  }
   PowerButtonController* power_button_controller() {
     return power_button_controller_.get();
   }
@@ -274,6 +271,7 @@ class ASH_EXPORT Shell {
   scoped_ptr<internal::ShadowController> shadow_controller_;
   scoped_ptr<internal::TooltipController> tooltip_controller_;
   scoped_ptr<internal::VisibilityController> visibility_controller_;
+  scoped_ptr<DesktopBackgroundController> desktop_background_controller_;
   scoped_ptr<PowerButtonController> power_button_controller_;
   scoped_ptr<VideoDetector> video_detector_;
   scoped_ptr<WindowCycleController> window_cycle_controller_;
@@ -304,9 +302,6 @@ class ASH_EXPORT Shell {
 
   ObserverList<ShellObserver> observers_;
 
-  // Can change at runtime.
-  BackgroundMode desktop_background_mode_;
-
   // Owned by aura::RootWindow, cached here for type safety.
   internal::RootWindowLayoutManager* root_window_layout_;