ElementAnimations should hold an ObservableList of AnimationPlayers.

cc/test/animation_timelines_test_common.h

 // Copyright 2015 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 CC_TEST_ANIMATION_TIMELINES_TEST_COMMON_H_
 #define CC_TEST_ANIMATION_TIMELINES_TEST_COMMON_H_
 
 #include <memory>
 #include <unordered_map>
 
@@ skipping 226 matching lines @@
                                TargetProperty::Type target_property,
                                int group) override;
   void NotifyAnimationAborted(base::TimeTicks monotonic_time,
                               TargetProperty::Type target_property,
                               int group) override;
   void NotifyAnimationTakeover(base::TimeTicks monotonic_time,
                                TargetProperty::Type target_property,
                                double animation_start_time,
                                std::unique_ptr<AnimationCurve> curve) override;
 
-  bool started() { return started_; }
+  int started() { return started_; }
 
-  bool finished() { return finished_; }
+  int finished() { return finished_; }
 
-  bool aborted() { return aborted_; }
+  int aborted() { return aborted_; }
 
-  bool takeover() { return takeover_; }
+  int takeover() { return takeover_; }
 
   base::TimeTicks start_time() { return start_time_; }
 
  private:
-  bool started_;
-  bool finished_;
-  bool aborted_;
-  bool takeover_;
+  int started_;
+  int finished_;
+  int aborted_;
+  int takeover_;
   base::TimeTicks start_time_;
 };
 
 class AnimationTimelinesTest : public testing::Test {
  public:
   AnimationTimelinesTest();
   ~AnimationTimelinesTest() override;
 
  protected:
   void SetUp() override;
@@ skipping 37 matching lines @@
   scoped_refptr<AnimationTimeline> timeline_;
   scoped_refptr<AnimationPlayer> player_;
 
   scoped_refptr<AnimationTimeline> timeline_impl_;
   scoped_refptr<AnimationPlayer> player_impl_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_ANIMATION_TIMELINES_TEST_COMMON_H_