Remove non-MD code from TrayBackgroundView

ash/common/system/chromeos/virtual_keyboard/virtual_keyboard_tray.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/common/system/chromeos/virtual_keyboard/virtual_keyboard_tray.h"
 
 #include <algorithm>
 
 #include "ash/common/keyboard/keyboard_ui.h"
 #include "ash/common/shelf/shelf_constants.h"
@@ skipping 11 matching lines @@
 #include "ui/keyboard/keyboard_controller.h"
 #include "ui/views/controls/image_view.h"
 
 namespace ash {
 
 VirtualKeyboardTray::VirtualKeyboardTray(WmShelf* wm_shelf)
     : TrayBackgroundView(wm_shelf),
       icon_(new views::ImageView),
       wm_shelf_(wm_shelf) {
   SetInkDropMode(InkDropMode::ON);
-  SetContentsBackground(false);
+  SetContentsBackground();
 
   icon_->SetImage(gfx::CreateVectorIcon(kShelfKeyboardIcon, kShelfIconColor));
   SetIconBorderForShelfAlignment();
   tray_container()->AddChildView(icon_);
 
   // The Shell may not exist in some unit tests.
   if (WmShell::HasInstance())
     WmShell::Get()->keyboard_ui()->AddObserver(this);
   // Try observing keyboard controller, in case it is already constructed.
   ObserveKeyboardController();
@@ skipping 73 matching lines @@
 }
 
 void VirtualKeyboardTray::UnobserveKeyboardController() {
   keyboard::KeyboardController* keyboard_controller =
       keyboard::KeyboardController::GetInstance();
   if (keyboard_controller)
     keyboard_controller->RemoveObserver(this);
 }
 
 }  // namespace ash