mash: Migrate wallpaper controllers to ash/common.

ash/test/test_wallpaper_delegate.cc

Index: ash/test/test_wallpaper_delegate.cc
diff --git a/ash/test/test_wallpaper_delegate.cc b/ash/test/test_wallpaper_delegate.cc
index 5b668be1228f73143f5ec833944de76c20b0c112..16279be13a161ccf25580533c8d275b0ef423631 100644
--- a/ash/test/test_wallpaper_delegate.cc
+++ b/ash/test/test_wallpaper_delegate.cc
@@ -4,8 +4,8 @@
 
 #include "ash/test/test_wallpaper_delegate.h"
 
-#include "ash/shell.h"
-#include "ash/wallpaper/wallpaper_controller.h"
+#include "ash/common/wallpaper/wallpaper_controller.h"
+#include "ash/common/wm_shell.h"
 
 namespace ash {
 namespace test {
@@ -17,7 +17,7 @@ TestWallpaperDelegate::~TestWallpaperDelegate() {}
 void TestWallpaperDelegate::UpdateWallpaper(bool clear_cache) {
   DefaultWallpaperDelegate::UpdateWallpaper(clear_cache);
   if (!custom_wallpaper_.isNull()) {
-    Shell::GetInstance()->wallpaper_controller()->SetWallpaperImage(
+    WmShell::Get()->wallpaper_controller()->SetWallpaperImage(
         custom_wallpaper_, wallpaper::WALLPAPER_LAYOUT_STRETCH);
   }
   update_wallpaper_count_++;