views: Make view::Views::GetPreferredSize() const.

ui/views/controls/scrollbar/native_scroll_bar.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/scrollbar/native_scroll_bar.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/message_loop/message_loop.h"
@@ skipping 24 matching lines @@
 }
 
 // static
 int NativeScrollBar::GetVerticalScrollBarWidth(
     const ui::NativeTheme* theme) {
   return NativeScrollBarWrapper::GetVerticalScrollBarWidth(theme);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeScrollBar, View overrides:
-gfx::Size NativeScrollBar::GetPreferredSize() {
+gfx::Size NativeScrollBar::GetPreferredSize() const {
   if (native_wrapper_)
     return native_wrapper_->GetView()->GetPreferredSize();
   return gfx::Size();
 }
 
 void NativeScrollBar::Layout() {
   if (native_wrapper_) {
     native_wrapper_->GetView()->SetBounds(0, 0, width(), height());
     native_wrapper_->GetView()->Layout();
   }
@@ skipping 49 matching lines @@
 }
 
 int NativeScrollBar::GetPosition() const {
   if (!native_wrapper_)
     return 0;
   return native_wrapper_->GetPosition();
 }
 
 }  // namespace views