ash: Remove old OEM wallpaper flags.

ash/desktop_background/desktop_background_controller.cc

Index: ash/desktop_background/desktop_background_controller.cc
diff --git a/ash/desktop_background/desktop_background_controller.cc b/ash/desktop_background/desktop_background_controller.cc
index 555739830674766c2501a181366f6f8a210e569c..2f4e6334ff3f250a068c535943cca452c49d5c6d 100644
--- a/ash/desktop_background/desktop_background_controller.cc
+++ b/ash/desktop_background/desktop_background_controller.cc
@@ -224,13 +224,8 @@ bool DesktopBackgroundController::SetDefaultWallpaper(bool is_guest) {
     switch_name = use_large ? switches::kAshGuestWallpaperLarge :
         switches::kAshGuestWallpaperSmall;
   } else {
-    const char* oem_switch_name = use_large ? switches::kAshOemWallpaperLarge :
-        switches::kAshOemWallpaperSmall;
-    const char* default_switch_name = use_large ?
-        switches::kAshDefaultWallpaperLarge :
+    switch_name = use_large ? switches::kAshDefaultWallpaperLarge :
         switches::kAshDefaultWallpaperSmall;
-    switch_name = command_line->HasSwitch(oem_switch_name) ? oem_switch_name :
-        default_switch_name;
   }
   file_path = command_line->GetSwitchValuePath(switch_name);