Only SchedulePaint on ShelfWidget if background changes.

ash/shelf/shelf_widget.cc

 // Copyright 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/shelf/shelf_widget.h"
 
 #include "ash/ash_switches.h"
 #include "ash/focus_cycler.h"
 #include "ash/root_window_controller.h"
 #include "ash/session/session_state_delegate.h"
@@ skipping 610 matching lines @@
     opaque_background_animation->SetTransitionDuration(
         base::TimeDelta::FromMilliseconds(wm::kTimeToSwitchBackgroundMs));
   }
   opaque_background->SetOpacity(target_opacity);
 
   // TODO(mukai): use ui::Layer on both opaque_background and normal background
   // retire background_animator_ at all. It would be simpler.
   // See also DockedBackgroundWidget::SetPaintsBackground.
   background_animator_.SetPaintsBackground(
       background_type != wm::SHELF_BACKGROUND_DEFAULT, change_type);
-  delegate_view_->SchedulePaint();
 }
 
 wm::ShelfBackgroundType ShelfWidget::GetBackgroundType() const {
   if (delegate_view_->opaque_background()->GetTargetOpacity() == 1.0f)
     return wm::SHELF_BACKGROUND_MAXIMIZED;
   if (background_animator_.paints_background())
     return wm::SHELF_BACKGROUND_OVERLAP;
 
   return wm::SHELF_BACKGROUND_DEFAULT;
 }
@@ skipping 146 matching lines @@
   DCHECK(delegate_view_);
   return delegate_view_->disable_dimming_animations_for_test();
 }
 
 void ShelfWidget::WillDeleteShelf() {
   shelf_layout_manager_->RemoveObserver(this);
   shelf_layout_manager_ = NULL;
 }
 
 }  // namespace ash