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

ash/frame/caption_buttons/frame_caption_button.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 "ash/frame/caption_buttons/frame_caption_button.h"
 
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/gfx/animation/slide_animation.h"
 #include "ui/gfx/animation/throb_animation.h"
 #include "ui/gfx/canvas.h"
@@ skipping 76 matching lines @@
     swap_images_animation_->Reset(1);
   }
   PreferredSizeChanged();
   SchedulePaint();
 }
 
 bool FrameCaptionButton::IsAnimatingImageSwap() const {
   return swap_images_animation_->is_animating();
 }
 
-gfx::Size FrameCaptionButton::GetPreferredSize() {
+gfx::Size FrameCaptionButton::GetPreferredSize() const {
   return hovered_background_image_.isNull() ?
       gfx::Size() : hovered_background_image_.size();
 }
 
 const char* FrameCaptionButton::GetClassName() const {
   return kViewClassName;
 }
 
 void FrameCaptionButton::OnPaint(gfx::Canvas* canvas) {
   if (hover_animation_->is_animating() || state() == STATE_HOVERED) {
@@ skipping 60 matching lines @@
                                        int alpha) {
   SkPaint paint;
   paint.setAlpha(alpha);
   canvas->DrawImageInt(to_center,
                        (width() - to_center.width()) / 2,
                        (height() - to_center.height()) / 2,
                        paint);
 }
 
 }  // namespace ash