CC Animation: Make AnimationPlayer to be a unit of activation.

cc/trees/layer_tree_host_unittest_animation.cc

Index: cc/trees/layer_tree_host_unittest_animation.cc
diff --git a/cc/trees/layer_tree_host_unittest_animation.cc b/cc/trees/layer_tree_host_unittest_animation.cc
index b6c4053e7b9b86057c6ac41cfa01d442dca3faee..cb659bc6c5a6fda340254d08a5ce5837d6a0d1b2 100644
--- a/cc/trees/layer_tree_host_unittest_animation.cc
+++ b/cc/trees/layer_tree_host_unittest_animation.cc
@@ -250,9 +250,8 @@ class LayerTreeHostAnimationTestAnimationsGetDeleted
 
   void AnimateLayers(LayerTreeHostImpl* host_impl,
                      base::TimeTicks monotonic_time) override {
-    bool have_animations = !GetImplAnimationHost(host_impl)
-                                ->active_element_animations_for_testing()
-                                .empty();
+    bool have_animations =
+        !GetImplAnimationHost(host_impl)->active_players_for_testing().empty();
     if (!started_animating_ && have_animations) {
       started_animating_ = true;
       return;
@@ -1366,9 +1365,9 @@ class LayerTreeHostAnimationTestAddAnimationAfterAnimating
   void CheckAnimations(LayerTreeHostImpl* host_impl) {
     GetImplTimelineAndPlayerByID(*host_impl);
 
-    EXPECT_EQ(2u, GetImplAnimationHost(host_impl)
-                      ->active_element_animations_for_testing()
-                      .size());
+    EXPECT_EQ(
+        2u,
+        GetImplAnimationHost(host_impl)->active_players_for_testing().size());
 
     Animation* root_anim =
         player_impl_->GetAnimation(TargetProperty::TRANSFORM);