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

ash/shell/panel_window.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 "ash/shell/panel_window.h"
 
 #include "ash/screen_util.h"
 #include "ash/shell.h"
 #include "ash/wm/panels/panel_frame_view.h"
 #include "base/strings/utf_string_conversions.h"
@@ skipping 39 matching lines @@
       Shell::GetTargetRootWindow(),
       params().bounds);
 
   widget->Init(params());
   widget->GetNativeView()->SetName(name_);
   widget->Show();
 
   return widget;
 }
 
-gfx::Size PanelWindow::GetPreferredSize() {
+gfx::Size PanelWindow::GetPreferredSize() const {
   return gfx::Size(kMinWidth, kMinHeight);
 }
 
 void PanelWindow::OnPaint(gfx::Canvas* canvas) {
   canvas->FillRect(GetLocalBounds(), SK_ColorGREEN);
 }
 
 base::string16 PanelWindow::GetWindowTitle() const {
   return base::ASCIIToUTF16(name_);
 }
 
 views::View* PanelWindow::GetContentsView() {
   return this;
 }
 
 bool PanelWindow::CanResize() const {
   return true;
 }
 
 bool PanelWindow::CanMaximize() const {
   return false;
 }
 
 views::NonClientFrameView* PanelWindow::CreateNonClientFrameView(
     views::Widget* widget) {
   return new PanelFrameView(widget, PanelFrameView::FRAME_NONE);
 }
 
 }  // namespace ash