CC Animation: Activate/deactivate ElementAnimations on Layer addition/removal.

cc/animation/element_animations.cc

 // 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.
 
 #include "cc/animation/element_animations.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 
@@ skipping 71 matching lines @@
   set_has_element_in_pending_list(false);
 
   animation_host_->DidDeactivateElementAnimations(this);
   UpdateActivation(FORCE_ACTIVATION);
 }
 
 void ElementAnimations::ElementRegistered(ElementId element_id,
                                           ElementListType list_type) {
   DCHECK_EQ(element_id_, element_id);
 
+  if (!has_element_in_any_list())
+    UpdateActivation(FORCE_ACTIVATION);
+
   if (list_type == ElementListType::ACTIVE)
     set_has_element_in_active_list(true);
   else
     set_has_element_in_pending_list(true);
 }
 
 void ElementAnimations::ElementUnregistered(ElementId element_id,
                                             ElementListType list_type) {
   DCHECK_EQ(this->element_id(), element_id);
   if (list_type == ElementListType::ACTIVE)
     set_has_element_in_active_list(false);
   else
     set_has_element_in_pending_list(false);
+
+  if (!has_element_in_any_list())
+    animation_host_->DidDeactivateElementAnimations(this);
 }
 
 void ElementAnimations::AddPlayer(AnimationPlayer* player) {
   players_list_->Append(player);
 }
 
 void ElementAnimations::RemovePlayer(AnimationPlayer* player) {
   for (PlayersListNode* node = players_list_->head();
        node != players_list_->end(); node = node->next()) {
     if (node->value() == player) {
@@ skipping 1315 matching lines @@
   if (animation_host()) {
     DCHECK(animation_host()->mutator_host_client());
     return animation_host()->mutator_host_client()->GetScrollOffsetForAnimation(
         element_id());
   }
 
   return gfx::ScrollOffset();
 }
 
 }  // namespace cc