[MD] Fix detached bookmark bar top separator in hdpi

chrome/browser/ui/views/bookmarks/bookmark_bar_view.cc

 // Copyright (c) 2012 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 "chrome/browser/ui/views/bookmarks/bookmark_bar_view.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 #include <limits>
@@ skipping 608 matching lines @@
       bookmark_bar_state_(BookmarkBar::SHOW),
       animating_detached_(false),
       show_folder_method_factory_(this) {
   set_id(VIEW_ID_BOOKMARK_BAR);
   Init();
 
   if (ui::MaterialDesignController::IsModeMaterial()) {
     // Don't let the bookmarks show on top of the location bar while animating.
     SetPaintToLayer(true);
     layer()->SetMasksToBounds(true);
+    layer()->SetFillsBoundsOpaquely(false);
   }
 
   size_animation_.Reset(1);
 }
 
 BookmarkBarView::~BookmarkBarView() {
   if (model_)
     model_->RemoveObserver(this);
 
   // It's possible for the menu to outlive us, reset the observer to make sure
@@ skipping 1523 matching lines @@
     return;
   apps_page_shortcut_->SetVisible(visible);
   UpdateBookmarksSeparatorVisibility();
   LayoutAndPaint();
 }
 
 void BookmarkBarView::OnShowManagedBookmarksPrefChanged() {
   if (UpdateOtherAndManagedButtonsVisibility())
     LayoutAndPaint();
 }