Refactoring button field and its type

content/renderer/webscrollbarbehavior_impl_mac.mm

 // 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 "content/renderer/webscrollbarbehavior_impl_mac.h"
 
 namespace content {
 
 WebScrollbarBehaviorImpl::WebScrollbarBehaviorImpl()
     : jump_on_track_click_(false) {
 }
 
 bool WebScrollbarBehaviorImpl::shouldCenterOnThumb(
-      blink::WebScrollbarBehavior::Button mouseButton,
+      blink::WebPointerProperties::Button mouseButton,
       bool shiftKeyPressed,
       bool altKeyPressed) {
-  return (mouseButton == blink::WebScrollbarBehavior::ButtonLeft) &&
+  return (mouseButton == blink::WebPointerProperties::Button::Left) &&
       (jump_on_track_click_ != altKeyPressed);
 }
 
 }  // namespace content