Fix regression where mouse hover effect is absent on the browser action chevron

chrome/browser/ui/views/toolbar/browser_actions_container.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 "chrome/browser/ui/views/toolbar/browser_actions_container.h"
 
 #include "base/compiler_specific.h"
 #include "base/stl_util.h"
 #include "chrome/browser/extensions/extension_action_manager.h"
 #include "chrome/browser/extensions/extension_util.h"
@@ skipping 156 matching lines @@
         this));
 
     resize_animation_.reset(new gfx::SlideAnimation(this));
     resize_area_ = new views::ResizeArea(this);
     AddChildView(resize_area_);
 
     // 'Main' mode doesn't need a chevron overflow when overflow is shown inside
     // the Chrome menu.
     if (!overflow_experiment) {
       chevron_ = new ChevronMenuButton(NULL, base::string16(), this, false);
-      chevron_->SetBorder(views::Border::NullBorder());
       chevron_->EnableCanvasFlippingForRTLUI(true);
       chevron_->SetAccessibleName(
           l10n_util::GetStringUTF16(IDS_ACCNAME_EXTENSIONS_CHEVRON));
       chevron_->SetVisible(false);
       AddChildView(chevron_);
     }
   }
 }
 
 BrowserActionsContainer::~BrowserActionsContainer() {
@@ skipping 912 matching lines @@
   size_t absolute_model_size =
       model_size == -1 ? extensions.size() : model_size;
 
   // The main container will try to show |model_size| icons, but reduce if there
   // aren't enough displayable icons to do so.
   size_t main_displayed = std::min(displayable_icon_count, absolute_model_size);
   // The overflow will display the extras, if any.
   return in_overflow_mode() ?
       displayable_icon_count - main_displayed : main_displayed;
 }