Use a bitfield to store animatable properties.

ash/wm/window_animations.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/wm/window_animations.h"
 
 #include <math.h>
 
 #include <algorithm>
 #include <vector>
@@ skipping 104 matching lines @@
   transition->set_tween_type(
       show ? gfx::Tween::EASE_IN : gfx::Tween::EASE_IN_OUT);
 
   window->layer()->GetAnimator()->ScheduleAnimation(
       new ui::LayerAnimationSequence(transition.release()));
 
   // When hiding a window, turn off blending until the animation is 3 / 4 done
   // to save bandwidth and reduce jank.
   if (!show) {
     window->layer()->GetAnimator()->SchedulePauseForProperties(
-        (duration * 3) / 4, ui::LayerAnimationElement::OPACITY, -1);
+        (duration * 3) / 4, ui::LayerAnimationElement::OPACITY);
   }
 
   // Fade in and out quickly when the window is small to reduce jank.
   float opacity = show ? 1.0f : 0.0f;
   window->layer()->GetAnimator()->ScheduleAnimation(
       new ui::LayerAnimationSequence(
           ui::LayerAnimationElement::CreateOpacityElement(
               opacity, duration / 4)));
 }
 
@@ skipping 405 matching lines @@
   }
 
   // Assume the shelf is overflowed, zoom off to the bottom right of the
   // work area.
   gfx::Rect work_area =
       Shell::GetScreen()->GetDisplayNearestWindow(window).work_area();
   return gfx::Rect(work_area.right(), work_area.bottom(), 0, 0);
 }
 
 }  // namespace ash