CC Animation: Let AnimationPlayer deals with elements.

Rename AttachLayer, DetachLayer and set_layer_animation_delegate methods.

BUG=510960
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review-Url: https://codereview.chromium.org/1916973006
Cr-Commit-Position: refs/heads/master@{#390245}
diff --git a/ui/compositor/layer_animator.cc b/ui/compositor/layer_animator.cc
index 1defb3f..b347496 100644
--- a/ui/compositor/layer_animator.cc
+++ b/ui/compositor/layer_animator.cc
@@ -192,18 +192,18 @@
 
 void LayerAnimator::AttachLayerToAnimationPlayer(int layer_id) {
   if (!animation_player_->element_id())
-    animation_player_->AttachLayer(layer_id);
+    animation_player_->AttachElement(layer_id);
   else
     DCHECK_EQ(animation_player_->element_id(), layer_id);
 
-  animation_player_->set_layer_animation_delegate(this);
+  animation_player_->set_animation_delegate(this);
 }
 
 void LayerAnimator::DetachLayerFromAnimationPlayer() {
-  animation_player_->set_layer_animation_delegate(nullptr);
+  animation_player_->set_animation_delegate(nullptr);
 
   if (animation_player_->element_id())
-    animation_player_->DetachLayer();
+    animation_player_->DetachElement();
 }
 
 void LayerAnimator::AddThreadedAnimation(