Remove non-MD code from overflow button and bubble

ash/common/shelf/overflow_bubble_view.cc

 // Copyright 2013 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/shelf/overflow_bubble_view.h"
 
 #include <algorithm>
 
 #include "ash/common/shelf/shelf_constants.h"
 #include "ash/common/shelf/wm_shelf.h"
@@ skipping 30 matching lines @@
 
 OverflowBubbleView::~OverflowBubbleView() {}
 
 void OverflowBubbleView::InitOverflowBubble(views::View* anchor,
                                             views::View* shelf_view) {
   shelf_view_ = shelf_view;
 
   SetAnchorView(anchor);
   set_arrow(GetBubbleArrow());
   set_mirror_arrow_in_rtl(false);
-  set_background(NULL);
+  set_background(nullptr);
   set_color(kShelfDefaultBaseColor);
   set_margins(gfx::Insets(kPadding, kPadding, kPadding, kPadding));
   // Overflow bubble should not get focus. If it get focus when it is shown,
   // active state item is changed to running state.
   set_can_activate(false);
 
   // Makes bubble view has a layer and clip its children layers.
   SetPaintToLayer();
   layer()->SetFillsBoundsOpaquely(false);
   layer()->SetMasksToBounds(true);
@@ skipping 159 matching lines @@
 
     bubble_rect.Offset(0, offset);
     border->set_arrow_offset(anchor_rect.CenterPoint().y() - bubble_rect.y());
   }
 
   GetBubbleFrameView()->SchedulePaint();
   return bubble_rect;
 }
 
 }  // namespace ash