Move all wallpaper file loading and decoding from DesktopBackgroundController to WallpaperManager.

ash/accelerators/debug_commands.cc

Index: ash/accelerators/debug_commands.cc
diff --git a/ash/accelerators/debug_commands.cc b/ash/accelerators/debug_commands.cc
index 4ca1720e3a00d581eebe5e70d3199d69d2488094..beca39fc41c0386bb4f5676bdb8e7b5c233e4f6a 100644
--- a/ash/accelerators/debug_commands.cc
+++ b/ash/accelerators/debug_commands.cc
@@ -44,17 +44,17 @@ bool CycleDesktopBackgroundMode() {
           InitializeWallpaper();
       break;
     case 1:
-      desktop_background_controller->SetCustomWallpaper(
+      desktop_background_controller->SetWallpaperImage(
           CreateWallpaperImage(SK_ColorRED, SK_ColorBLUE),
           WALLPAPER_LAYOUT_STRETCH);
       break;
     case 2:
-      desktop_background_controller->SetCustomWallpaper(
+      desktop_background_controller->SetWallpaperImage(
           CreateWallpaperImage(SK_ColorBLUE, SK_ColorGREEN),
           WALLPAPER_LAYOUT_CENTER);
       break;
     case 3:
-      desktop_background_controller->SetCustomWallpaper(
+      desktop_background_controller->SetWallpaperImage(
           CreateWallpaperImage(SK_ColorGREEN, SK_ColorRED),
           WALLPAPER_LAYOUT_CENTER_CROPPED);
       break;