Use a bitfield to store animatable properties.

ui/compositor/layer_animation_observer.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 "ui/compositor/layer_animation_observer.h"
 
 #include "ui/compositor/layer_animation_sequence.h"
 
 namespace ui {
 
@@ skipping 122 matching lines @@
 void ImplicitAnimationObserver::CheckCompleted() {
   if (active_ && attached_sequences().empty()) {
     active_ = false;
     OnImplicitAnimationsCompleted();
   }
 }
 
 void ImplicitAnimationObserver::UpdatePropertyAnimationStatus(
     LayerAnimationSequence* sequence,
     AnimationStatus status) {
-  const LayerAnimationElement::AnimatableProperties& properties =
+  LayerAnimationElement::AnimatableProperties properties =
       sequence->properties();
-  for (LayerAnimationElement::AnimatableProperties::const_iterator i =
-           properties.begin(); i != properties.end(); ++i) {
-    property_animation_status_[(*i)] = status;
+  for (unsigned i = LayerAnimationElement::FIRST_PROPERTY;
+       i != LayerAnimationElement::SENTINEL;
+       i = i << 1) {
+    if (i & properties) {
+      LayerAnimationElement::AnimatableProperty property =
+          static_cast<LayerAnimationElement::AnimatableProperty>(i);
+      property_animation_status_[property] = status;
+    }
   }
 }
 
 ImplicitAnimationObserver::AnimationStatus
 ImplicitAnimationObserver::AnimationStatusForProperty(
     LayerAnimationElement::AnimatableProperty property) const {
   PropertyAnimationStatusMap::const_iterator iter =
       property_animation_status_.find(property);
   return iter == property_animation_status_.end() ? ANIMATION_STATUS_UNKNOWN :
       iter->second;
 }
 
 }  // namespace ui