Use a bitfield to store animatable properties.

ash/shelf/app_list_button.cc

Index: ash/shelf/app_list_button.cc
diff --git a/ash/shelf/app_list_button.cc b/ash/shelf/app_list_button.cc
index 673ed11be9418a0bf1a0d9500338808565896e74..3fef94a5c78489da8bbe67c8dd1fc9168a2d99ac 100644
--- a/ash/shelf/app_list_button.cc
+++ b/ash/shelf/app_list_button.cc
@@ -67,11 +67,9 @@ void AppListButton::StartLoadingAnimation() {
             base::TimeDelta::FromMilliseconds(kAnimationDurationInMs)));
   }
 
-  ui::LayerAnimationElement::AnimatableProperties opacity_properties;
-  opacity_properties.insert(ui::LayerAnimationElement::OPACITY);
   opacity_sequence->AddElement(
       ui::LayerAnimationElement::CreatePauseElement(
-          opacity_properties,
+          ui::LayerAnimationElement::OPACITY,
           base::TimeDelta::FromMilliseconds(kAnimationDurationInMs)));
 
   // LayerAnimator takes ownership of the sequences.