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

ash/system/tray/throbber_view.cc

 // Copyright (c) 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/system/tray/throbber_view.h"
 
 #include "ash/system/tray/tray_constants.h"
 #include "grit/ash_resources.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/compositor/layer.h"
@@ skipping 38 matching lines @@
   AddChildView(throbber_);
 
   SetPaintToLayer(true);
   layer()->SetFillsBoundsOpaquely(false);
   layer()->SetOpacity(0.0);
 }
 
 ThrobberView::~ThrobberView() {
 }
 
-gfx::Size ThrobberView::GetPreferredSize() {
+gfx::Size ThrobberView::GetPreferredSize() const {
   return gfx::Size(ash::kTrayPopupItemHeight, ash::kTrayPopupItemHeight);
 }
 
 void ThrobberView::Layout() {
   View* child = child_at(0);
   gfx::Size ps = child->GetPreferredSize();
   child->SetBounds((width() - ps.width()) / 2,
                    (height() - ps.height()) / 2,
                    ps.width(), ps.height());
   SizeToPreferredSize();
@@ skipping 28 matching lines @@
   layer()->GetAnimator()->StopAnimating();
 
   ui::ScopedLayerAnimationSettings animation(layer()->GetAnimator());
   animation.SetTransitionDuration(
       base::TimeDelta::FromMilliseconds(kThrobberAnimationDurationMs));
 
   layer()->SetOpacity(start_throbber ? 1.0 : 0.0);
 }
 
 }  // namespace ash