LabelButton: cache the last computed preferred size

ash/system/chromeos/session/logout_button_tray.cc

 // Copyright 2014 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/chromeos/session/logout_button_tray.h"
 
 #include "ash/shelf/shelf_types.h"
 #include "ash/shell.h"
 #include "ash/system/chromeos/session/logout_confirmation_controller.h"
 #include "ash/system/status_area_widget.h"
@@ skipping 68 matching lines @@
       views::Painter::CreateImageGridPainter(kLogoutButtonNormalImages));
   border->SetPainter(false, views::Button::STATE_PRESSED,
       views::Painter::CreateImageGridPainter(kLogoutButtonPushedImages));
   gfx::Insets insets = border->GetInsets();
   insets += gfx::Insets(0, kLogoutButtonHorizontalExtraPadding,
                         0, kLogoutButtonHorizontalExtraPadding);
   border->set_insets(insets);
   SetBorder(border.PassAs<views::Border>());
   set_animate_on_state_change(false);
 
-  set_min_size(gfx::Size(0, kShelfItemHeight));
+  SetMinSize(gfx::Size(0, kShelfItemHeight));
 }
 
 LogoutButton::~LogoutButton() {
 }
 
 LogoutButtonTray::LogoutButtonTray(StatusAreaWidget* status_area_widget)
     : TrayBackgroundView(status_area_widget),
       button_(NULL),
       login_status_(user::LOGGED_IN_NONE),
       show_logout_button_in_tray_(false) {
@@ skipping 56 matching lines @@
   UpdateVisibility();
 }
 
 void LogoutButtonTray::UpdateVisibility() {
   SetVisible(show_logout_button_in_tray_ &&
              login_status_ != user::LOGGED_IN_NONE &&
              login_status_ != user::LOGGED_IN_LOCKED);
 }
 
 }  // namespace ash