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

ui/views/test/test_views.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 "ui/views/test/test_views.h"
 
 namespace views {
 
 StaticSizedView::StaticSizedView(const gfx::Size& size) : size_(size) {}
 
 StaticSizedView::~StaticSizedView() {}
 
-gfx::Size StaticSizedView::GetPreferredSize() {
+gfx::Size StaticSizedView::GetPreferredSize() const {
   return size_;
 }
 
 ProportionallySizedView::ProportionallySizedView(int factor)
     : factor_(factor) {}
 
 ProportionallySizedView::~ProportionallySizedView() {}
 
-int ProportionallySizedView::GetHeightForWidth(int w) {
+int ProportionallySizedView::GetHeightForWidth(int w) const {
   return w * factor_;
 }
 
 }  // namespace views