ElementAnimations should hold an ObservableList of AnimationPlayers.

cc/test/animation_timelines_test_common.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/test/animation_timelines_test_common.h"
 
 #include "base/memory/ptr_util.h"
 #include "cc/animation/animation_events.h"
 #include "cc/animation/animation_id_provider.h"
 #include "cc/animation/animation_player.h"
@@ skipping 337 matching lines @@
                                            : layers_in_pending_tree_;
   auto kv = layers_in_tree.find(element_id);
   if (kv == layers_in_tree.end())
     return nullptr;
 
   DCHECK(kv->second);
   return kv->second.get();
 }
 
 TestAnimationDelegate::TestAnimationDelegate()
-    : started_(false),
-      finished_(false),
-      aborted_(false),
-      takeover_(false),
+    : started_(0),
+      finished_(0),
+      aborted_(0),
+      takeover_(0),
       start_time_(base::TimeTicks()) {}
 
 void TestAnimationDelegate::NotifyAnimationStarted(
     base::TimeTicks monotonic_time,
     TargetProperty::Type target_property,
     int group) {
-  started_ = true;
+  started_++;
   start_time_ = monotonic_time;
 }
 
 void TestAnimationDelegate::NotifyAnimationFinished(
     base::TimeTicks monotonic_time,
     TargetProperty::Type target_property,
     int group) {
-  finished_ = true;
+  finished_++;
 }
 
 void TestAnimationDelegate::NotifyAnimationAborted(
     base::TimeTicks monotonic_time,
     TargetProperty::Type target_property,
     int group) {
-  aborted_ = true;
+  aborted_++;
 }
 
 void TestAnimationDelegate::NotifyAnimationTakeover(
     base::TimeTicks monotonic_time,
     TargetProperty::Type target_property,
     double animation_start_time,
     std::unique_ptr<AnimationCurve> curve) {
-  takeover_ = true;
+  takeover_++;
 }
 
 AnimationTimelinesTest::AnimationTimelinesTest()
     : client_(ThreadInstance::MAIN),
       client_impl_(ThreadInstance::IMPL),
       host_(nullptr),
       host_impl_(nullptr),
       timeline_id_(AnimationIdProvider::NextTimelineId()),
       player_id_(AnimationIdProvider::NextPlayerId()),
       next_test_layer_id_(0) {
@@ skipping 86 matching lines @@
 
   host_->AnimateLayers(time);
   host_->UpdateAnimationState(true, nullptr);
   host_->SetAnimationEvents(std::move(events));
 }
 
 AnimationPlayer* AnimationTimelinesTest::GetPlayerForElementId(
     ElementId element_id) {
   const scoped_refptr<ElementAnimations> element_animations =
       host_->GetElementAnimationsForElementId(element_id);
-  return element_animations ? element_animations->players_list().head()->value()
-                            : nullptr;
+  return element_animations
+             ? base::ObserverList<AnimationPlayer>::Iterator(
+                   &element_animations->players_list())
+                   .GetNext()
+             : nullptr;
 }
 
 AnimationPlayer* AnimationTimelinesTest::GetImplPlayerForLayerId(
     ElementId element_id) {
   const scoped_refptr<ElementAnimations> element_animations =
       host_impl_->GetElementAnimationsForElementId(element_id);
-  return element_animations ? element_animations->players_list().head()->value()
-                            : nullptr;
+  return element_animations
+             ? base::ObserverList<AnimationPlayer>::Iterator(
+                   &element_animations->players_list())
+                   .GetNext()
+             : nullptr;
 }
 
 int AnimationTimelinesTest::NextTestLayerId() {
   next_test_layer_id_++;
   return next_test_layer_id_;
 }
 
 }  // namespace cc