Use a bitfield to store animatable properties.

ash/wm/window_animations.cc

Index: ash/wm/window_animations.cc
diff --git a/ash/wm/window_animations.cc b/ash/wm/window_animations.cc
index 71d73f353c6f987d38246090a470a38b9b5a6b19..ae7188a323f1b1a58a8a2b44cee44cc815e2d99f 100644
--- a/ash/wm/window_animations.cc
+++ b/ash/wm/window_animations.cc
@@ -122,7 +122,7 @@ void AddLayerAnimationsForMinimize(aura::Window* window, bool show) {
   // 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.