Introduces a new scrollbar for message_center.

ui/views/controls/scrollbar/scroll_bar.cc

 // Copyright (c) 2011 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/scrollbar/scroll_bar.h"
 
 #include "ui/base/accessibility/accessible_view_state.h"
 
 namespace views {
 
@@ skipping 13 matching lines @@
 }
 
 int ScrollBar::GetMaxPosition() const {
   return max_pos_;
 }
 
 int ScrollBar::GetMinPosition() const {
   return 0;
 }
 
+int ScrollBar::GetVisibleSize() const {
+  return GetLayoutSize();
+}
+
+void ScrollBar::OnMouseEnteredScrollView(const ui::MouseEvent& event) {
+}
+
+void ScrollBar::OnMouseExitedScrollView(const ui::MouseEvent& event) {
+}
+
 ScrollBar::ScrollBar(bool is_horiz)
     : is_horiz_(is_horiz),
       controller_(NULL),
       max_pos_(0) {
 }
 
 }  // namespace views