Use a bitfield to store animatable properties.

ui/compositor/layer_animation_sequence.h

 // 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.
 
 #ifndef UI_COMPOSITOR_LAYER_ANIMATION_SEQUENCE_H_
 #define UI_COMPOSITOR_LAYER_ANIMATION_SEQUENCE_H_
 
 #include <vector>
 
 #include "base/gtest_prod_util.h"
@@ skipping 63 matching lines @@
   void ProgressToEnd(LayerAnimationDelegate* delegate);
 
   // Sets the target value to the value that would have been set had
   // the sequence completed. Does nothing if the sequence is cyclic.
   void GetTargetValue(LayerAnimationElement::TargetValue* target) const;
 
   // Aborts the given animation.
   void Abort(LayerAnimationDelegate* delegate);
 
   // All properties modified by the sequence.
-  const LayerAnimationElement::AnimatableProperties& properties() const {
+  LayerAnimationElement::AnimatableProperties properties() const {
     return properties_;
   }
 
   // Adds an element to the sequence. The sequences takes ownership of this
   // element.
   void AddElement(LayerAnimationElement* element);
 
   // Sequences can be looped indefinitely.
   void set_is_cyclic(bool is_cyclic) { is_cyclic_ = is_cyclic; }
   bool is_cyclic() const { return is_cyclic_; }
 
   // Returns true if this sequence has at least one element conflicting with a
   // property in |other|.
   bool HasConflictingProperty(
-      const LayerAnimationElement::AnimatableProperties& other) const;
+      LayerAnimationElement::AnimatableProperties other) const;
 
   // Returns true if the first element animates on the compositor thread.
   bool IsFirstElementThreaded() const;
 
   // Used to identify groups of sequences that are supposed to start together.
   // Once started, used to identify the sequence that owns a particular
   // threaded animation.
   int animation_group_id() const { return animation_group_id_; }
   void set_animation_group_id(int id) { animation_group_id_ = id; }
 
@@ skipping 73 matching lines @@
   double last_progressed_fraction_;
 
   base::WeakPtrFactory<LayerAnimationSequence> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(LayerAnimationSequence);
 };
 
 }  // namespace ui
 
 #endif  // UI_COMPOSITOR_LAYER_ANIMATION_SEQUENCE_H_