Add the button style for combobox

ui/views/controls/button/custom_button.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 "ui/views/controls/button/custom_button.h"
 
 #include "ui/base/accessibility/accessible_view_state.h"
 #include "ui/events/event.h"
 #include "ui/events/keycodes/keyboard_codes.h"
 #include "ui/gfx/animation/throb_animation.h"
 #include "ui/gfx/screen.h"
 #include "ui/views/widget/widget.h"
 
 namespace views {
 
-// How long the hover animation takes if uninterrupted.
-static const int kHoverFadeDurationMs = 150;
+// static
+const int CustomButton::kHoverFadeDurationMs = 150;
 
 // static
 const char CustomButton::kViewClassName[] = "CustomButton";
 
 ////////////////////////////////////////////////////////////////////////////////
 // CustomButton, public:
 
 CustomButton::~CustomButton() {
 }
 
@@ skipping 291 matching lines @@
   if (!details.is_add && state_ != STATE_DISABLED)
     SetState(STATE_NORMAL);
 }
 
 void CustomButton::OnBlur() {
   if (IsHotTracked())
     SetState(STATE_NORMAL);
 }
 
 }  // namespace views