Remove non-MD code from TrayBackgroundView

ash/common/system/chromeos/ime_menu/ime_menu_tray.cc

Index: ash/common/system/chromeos/ime_menu/ime_menu_tray.cc
diff --git a/ash/common/system/chromeos/ime_menu/ime_menu_tray.cc b/ash/common/system/chromeos/ime_menu/ime_menu_tray.cc
index 90653113bbdd5b6ef3915f6b7c608fa80b42ced0..40be0de319c5b857371ab80b684328a77e601fdb 100644
--- a/ash/common/system/chromeos/ime_menu/ime_menu_tray.cc
+++ b/ash/common/system/chromeos/ime_menu/ime_menu_tray.cc
@@ -362,12 +362,9 @@ ImeMenuTray::ImeMenuTray(WmShelf* wm_shelf)
       should_block_shelf_auto_hide_(false),
       keyboard_suppressed_(false),
       show_bubble_after_keyboard_hidden_(false) {
-  if (MaterialDesignController::IsShelfMaterial()) {
+  if (MaterialDesignController::IsShelfMaterial())
     SetInkDropMode(InkDropMode::ON);
-    SetContentsBackground(false);
-  } else {
-    SetContentsBackground(true);
-  }
+  SetContentsBackground();
   SetupLabelForTray(label_);
   tray_container()->AddChildView(label_);
   SystemTrayNotifier* tray_notifier = WmShell::Get()->system_tray_notifier();