Use a bitfield to store animatable properties.

ui/compositor/test/layer_animator_test_controller.cc

 // Copyright (c) 2013 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 "cc/animation/animation.h"
 #include "ui/compositor/layer_animation_sequence.h"
 #include "ui/compositor/test/layer_animator_test_controller.h"
 #include "ui/gfx/frame_time.h"
 #include "ui/gfx/rect.h"
 
@@ skipping 23 matching lines @@
   threaded_properties.push_back(cc::Animation::Transform);
 
   for (size_t i = 0; i < threaded_properties.size(); i++) {
     LayerAnimationElement::AnimatableProperty animatable_property =
         LayerAnimationElement::ToAnimatableProperty(threaded_properties[i]);
     LayerAnimationSequence* sequence = GetRunningSequence(animatable_property);
     if (!sequence)
       continue;
 
     LayerAnimationElement* element = sequence->CurrentElement();
-    if (element->properties().find(animatable_property) ==
-        element->properties().end())
+    if (!(element->properties() & animatable_property))
       continue;
 
     if (!element->Started() ||
         element->effective_start_time() != base::TimeTicks())
       continue;
 
     animator_->OnThreadedAnimationStarted(cc::AnimationEvent(
         cc::AnimationEvent::Started,
         0,
         element->animation_group_id(),
         threaded_properties[i],
         (gfx::FrameTime::Now() - base::TimeTicks()).InSecondsF()));
   }
 }
 
 }  // namespace ui