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

ash/accelerators/accelerator_controller.cc

Index: ash/accelerators/accelerator_controller.cc
diff --git a/ash/accelerators/accelerator_controller.cc b/ash/accelerators/accelerator_controller.cc
index 0eb7ce809b2fbf83cd01dd3bd441bd0f2bdfb654..b43b5f4858809c4a87dc4bfa5d79a048c6646238 100644
--- a/ash/accelerators/accelerator_controller.cc
+++ b/ash/accelerators/accelerator_controller.cc
@@ -5,6 +5,7 @@
 #include "ash/accelerators/accelerator_controller.h"
 
 #include "ash/accelerators/accelerator_table.h"
+#include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/ash_switches.h"
 #include "ash/caps_lock_delegate.h"
 #include "ash/ime_control_delegate.h"
@@ -90,11 +91,13 @@ bool HandleRotateScreen() {
 }
 
 bool HandleToggleDesktopBackgroundMode() {
-  ash::Shell* shell = ash::Shell::GetInstance();
-  if (shell->desktop_background_mode() == ash::Shell::BACKGROUND_IMAGE)
-    shell->SetDesktopBackgroundMode(ash::Shell::BACKGROUND_SOLID_COLOR);
+  ash::DesktopBackgroundController* desktop_background_controller =
+      ash::Shell::GetInstance()->desktop_background_controller();
+  if (desktop_background_controller->desktop_background_mode() ==
+      ash::DesktopBackgroundController::BACKGROUND_IMAGE)
+    desktop_background_controller->SetDesktopBackgroundSolidColorMode();
   else
-    shell->SetDesktopBackgroundMode(ash::Shell::BACKGROUND_IMAGE);
+    desktop_background_controller->SetPreviousDesktopBackgroundImage();
   return true;
 }