CC Animation: Move animations_ from ElementAnimations to AnimationPlayer.

cc/animation/element_animations.cc

Index: cc/animation/element_animations.cc
diff --git a/cc/animation/element_animations.cc b/cc/animation/element_animations.cc
index b1bd59e03a808fee891acdf2864d5f87255a83bb..35de36725d0732d55d31f11a50e2434867524243 100644
--- a/cc/animation/element_animations.cc
+++ b/cc/animation/element_animations.cc
@@ -14,7 +14,6 @@
 #include "cc/animation/animation_host.h"
 #include "cc/animation/animation_player.h"
 #include "cc/animation/keyframed_animation_curve.h"
-#include "cc/animation/scroll_offset_animation_curve.h"
 #include "cc/output/filter_operations.h"
 #include "cc/trees/mutator_host_client.h"
 #include "ui/gfx/geometry/box_f.h"
@@ -32,9 +31,10 @@ ElementAnimations::ElementAnimations()
       is_active_(false),
       has_element_in_active_list_(false),
       has_element_in_pending_list_(false),
-      needs_to_start_animations_(false),
       scroll_offset_animation_was_interrupted_(false),
-      needs_push_properties_(false) {}
+      needs_push_properties_(false) {
+  ClearNeedsUpdateImplClientState();
+}
 
 ElementAnimations::~ElementAnimations() {}
 
@@ -50,7 +50,7 @@ void ElementAnimations::InitAffectedElementTypes() {
   DCHECK(element_id_);
   DCHECK(animation_host_);
 
-  UpdateActivation(FORCE_ACTIVATION);
+  UpdateActivation(ActivationType::FORCE);
 
   DCHECK(animation_host_->mutator_host_client());
   if (animation_host_->mutator_host_client()->IsElementInList(
@@ -83,7 +83,7 @@ void ElementAnimations::ClearAffectedElementTypes() {
   set_has_element_in_pending_list(false);
 
   animation_host_->DidDeactivateElementAnimations(this);
-  UpdateActivation(FORCE_ACTIVATION);
+  UpdateActivation(ActivationType::FORCE);
 }
 
 void ElementAnimations::ElementRegistered(ElementId element_id,
@@ -91,7 +91,7 @@ void ElementAnimations::ElementRegistered(ElementId element_id,
   DCHECK_EQ(element_id_, element_id);
 
   if (!has_element_in_any_list())
-    UpdateActivation(FORCE_ACTIVATION);
+    UpdateActivation(ActivationType::FORCE);
 
   if (list_type == ElementListType::ACTIVE)
     set_has_element_in_active_list(true);
@@ -135,39 +135,56 @@ void ElementAnimations::PushPropertiesTo(
     return;
   needs_push_properties_ = false;
 
-  if (!HasAnyAnimation() && !element_animations_impl->HasAnyAnimation())
-    return;
-  MarkAbortedAnimationsForDeletion(element_animations_impl.get());
-  PurgeAnimationsMarkedForDeletion();
-  PushNewAnimationsToImplThread(element_animations_impl.get());
-
-  // Remove finished impl side animations only after pushing,
-  // and only after the animations are deleted on the main thread
-  // this insures we will never push an animation twice.
-  RemoveAnimationsCompletedOnMainThread(element_animations_impl.get());
-
-  PushPropertiesToImplThread(element_animations_impl.get());
-  element_animations_impl->UpdateActivation(NORMAL_ACTIVATION);
-  UpdateActivation(NORMAL_ACTIVATION);
+  element_animations_impl->scroll_offset_animation_was_interrupted_ =
+      scroll_offset_animation_was_interrupted_;
+  scroll_offset_animation_was_interrupted_ = false;
+
+  // Update impl client state.
+  element_animations_impl->UpdateClientAnimationState(
+      needs_update_impl_client_state_transform_,
+      needs_update_impl_client_state_opacity_,
+      needs_update_impl_client_state_filter_);
+  ClearNeedsUpdateImplClientState();
+
+  element_animations_impl->UpdateActivation(ActivationType::NORMAL);
+  UpdateActivation(ActivationType::NORMAL);
 }
 
-void ElementAnimations::AddAnimation(std::unique_ptr<Animation> animation) {
-  DCHECK(!animation->is_impl_only() ||
-         animation->target_property() == TargetProperty::SCROLL_OFFSET);
-  TargetProperty::Type target_property = animation->target_property();
-  animations_.push_back(std::move(animation));
-  needs_to_start_animations_ = true;
-  UpdateActivation(NORMAL_ACTIVATION);
+void ElementAnimations::UpdateClientAnimationState(
+    TargetProperty::Type target_property) {
   switch (target_property) {
     case TargetProperty::TRANSFORM:
     case TargetProperty::OPACITY:
     case TargetProperty::FILTER:
-      UpdateClientAnimationState(target_property);
+      UpdateClientAnimationStateInternal(target_property);
       break;
     default:
+      // Do not update for other properties.
       break;
   }
-  SetNeedsPushProperties();
+}
+
+void ElementAnimations::UpdateClientAnimationState(bool transform,
+                                                   bool opacity,
+                                                   bool filter) {
+  if (transform)
+    UpdateClientAnimationStateInternal(TargetProperty::TRANSFORM);
+  if (opacity)
+    UpdateClientAnimationStateInternal(TargetProperty::OPACITY);
+  if (filter)
+    UpdateClientAnimationStateInternal(TargetProperty::FILTER);
+}
+
+void ElementAnimations::AddAnimation(std::unique_ptr<Animation> animation) {
+  // TODO(loyso): Erase this. Rewrite element_animations_unittest to use
+  // AnimationPlayer::AddAnimation.
+
+  // Add animation to the first player.
+  DCHECK(players_list_->might_have_observers());
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player = it.GetNext();
+  DCHECK(player);
+  player->AddAnimation(std::move(animation));
 }
 
 void ElementAnimations::Animate(base::TimeTicks monotonic_time) {
@@ -175,13 +192,27 @@ void ElementAnimations::Animate(base::TimeTicks monotonic_time) {
   if (!has_element_in_active_list() && !has_element_in_pending_list())
     return;
 
-  if (needs_to_start_animations_)
-    StartAnimations(monotonic_time);
-  TickAnimations(monotonic_time);
+  {
+    // TODO(crbug.com/634916): Shouldn't manually iterate through the list if
+    // base::ObserverList has a callback mechanism.
+    ElementAnimations::PlayersList::Iterator it(players_list_.get());
+    AnimationPlayer* player;
+    while ((player = it.GetNext()) != nullptr) {
+      if (player->needs_to_start_animations())
+        player->StartAnimations(monotonic_time);
+    }
+  }
+  {
+    ElementAnimations::PlayersList::Iterator it(players_list_.get());
+    AnimationPlayer* player;
+    while ((player = it.GetNext()) != nullptr)
+      player->TickAnimations(monotonic_time);
+  }
   last_tick_time_ = monotonic_time;
-  UpdateClientAnimationState(TargetProperty::OPACITY);
-  UpdateClientAnimationState(TargetProperty::TRANSFORM);
-  UpdateClientAnimationState(TargetProperty::FILTER);
+
+  UpdateClientAnimationStateInternal(TargetProperty::OPACITY);
+  UpdateClientAnimationStateInternal(TargetProperty::TRANSFORM);
+  UpdateClientAnimationStateInternal(TargetProperty::FILTER);
 }
 
 void ElementAnimations::UpdateState(bool start_ready_animations,
@@ -194,130 +225,106 @@ void ElementAnimations::UpdateState(bool start_ready_animations,
   if (last_tick_time_ == base::TimeTicks())
     return;
 
-  if (start_ready_animations)
-    PromoteStartedAnimations(last_tick_time_, events);
-
-  MarkFinishedAnimations(last_tick_time_);
-  MarkAnimationsForDeletion(last_tick_time_, events);
-
-  if (needs_to_start_animations_ && start_ready_animations) {
-    StartAnimations(last_tick_time_);
-    PromoteStartedAnimations(last_tick_time_, events);
+  if (start_ready_animations) {
+    ElementAnimations::PlayersList::Iterator it(players_list_.get());
+    AnimationPlayer* player;
+    while ((player = it.GetNext()) != nullptr)
+      player->PromoteStartedAnimations(last_tick_time_, events);
+  }
+
+  {
+    ElementAnimations::PlayersList::Iterator it(players_list_.get());
+    AnimationPlayer* player;
+    while ((player = it.GetNext()) != nullptr)
+      player->MarkFinishedAnimations(last_tick_time_);
+  }
+  {
+    ElementAnimations::PlayersList::Iterator it(players_list_.get());
+    AnimationPlayer* player;
+    while ((player = it.GetNext()) != nullptr)
+      player->MarkAnimationsForDeletion(last_tick_time_, events);
+  }
+
+  if (start_ready_animations) {
+    ElementAnimations::PlayersList::Iterator it(players_list_.get());
+    AnimationPlayer* player;
+    while ((player = it.GetNext()) != nullptr) {
+      if (player->needs_to_start_animations()) {
+        player->StartAnimations(last_tick_time_);
+        player->PromoteStartedAnimations(last_tick_time_, events);
+      }
+    }
   }
 
-  UpdateActivation(NORMAL_ACTIVATION);
+  UpdateActivation(ActivationType::NORMAL);
 }
 
 void ElementAnimations::ActivateAnimations() {
   bool changed_transform_animation = false;
   bool changed_opacity_animation = false;
   bool changed_filter_animation = false;
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->affects_active_elements() !=
-        animations_[i]->affects_pending_elements()) {
-      if (animations_[i]->target_property() == TargetProperty::TRANSFORM)
-        changed_transform_animation = true;
-      else if (animations_[i]->target_property() == TargetProperty::OPACITY)
-        changed_opacity_animation = true;
-      else if (animations_[i]->target_property() == TargetProperty::FILTER)
-        changed_filter_animation = true;
-    }
-    animations_[i]->set_affects_active_elements(
-        animations_[i]->affects_pending_elements());
+
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    player->ActivateAnimations(&changed_transform_animation,
+                               &changed_opacity_animation,
+                               &changed_filter_animation);
   }
-  auto affects_no_elements = [](const std::unique_ptr<Animation>& animation) {
-    return !animation->affects_active_elements() &&
-           !animation->affects_pending_elements();
-  };
-  animations_.erase(std::remove_if(animations_.begin(), animations_.end(),
-                                   affects_no_elements),
-                    animations_.end());
+
   scroll_offset_animation_was_interrupted_ = false;
-  UpdateActivation(NORMAL_ACTIVATION);
-  if (changed_transform_animation)
-    UpdateClientAnimationState(TargetProperty::TRANSFORM);
-  if (changed_opacity_animation)
-    UpdateClientAnimationState(TargetProperty::OPACITY);
-  if (changed_filter_animation)
-    UpdateClientAnimationState(TargetProperty::FILTER);
+  UpdateActivation(ActivationType::NORMAL);
+  UpdateClientAnimationState(changed_transform_animation,
+                             changed_opacity_animation,
+                             changed_filter_animation);
 }
 
 void ElementAnimations::NotifyAnimationStarted(const AnimationEvent& event) {
-  if (event.is_impl_only) {
-    NotifyPlayersAnimationStarted(event.monotonic_time, event.target_property,
-                                  event.group_id);
-    return;
-  }
-
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->group() == event.group_id &&
-        animations_[i]->target_property() == event.target_property &&
-        animations_[i]->needs_synchronized_start_time()) {
-      animations_[i]->set_needs_synchronized_start_time(false);
-      if (!animations_[i]->has_set_start_time())
-        animations_[i]->set_start_time(event.monotonic_time);
-
-      NotifyPlayersAnimationStarted(event.monotonic_time, event.target_property,
-                                    event.group_id);
-
-      return;
-    }
+  DCHECK(!event.is_impl_only);
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->NotifyAnimationStarted(event))
+      break;
   }
 }
 
 void ElementAnimations::NotifyAnimationFinished(const AnimationEvent& event) {
-  if (event.is_impl_only) {
-    NotifyPlayersAnimationFinished(event.monotonic_time, event.target_property,
-                                   event.group_id);
-    return;
-  }
-
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->group() == event.group_id &&
-        animations_[i]->target_property() == event.target_property) {
-      animations_[i]->set_received_finished_event(true);
-      NotifyPlayersAnimationFinished(event.monotonic_time,
-                                     event.target_property, event.group_id);
-
-      return;
-    }
+  DCHECK(!event.is_impl_only);
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->NotifyAnimationFinished(event))
+      break;
   }
 }
 
 void ElementAnimations::NotifyAnimationTakeover(const AnimationEvent& event) {
+  DCHECK(!event.is_impl_only);
   DCHECK(event.target_property == TargetProperty::SCROLL_OFFSET);
-  if (!IsEmpty()) {
-    std::unique_ptr<AnimationCurve> animation_curve = event.curve->Clone();
-    NotifyPlayersAnimationTakeover(event.monotonic_time, event.target_property,
-                                   event.animation_start_time,
-                                   std::move(animation_curve));
-  }
+
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr)
+    player->NotifyAnimationTakeover(event);
 }
 
 void ElementAnimations::NotifyAnimationAborted(const AnimationEvent& event) {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->group() == event.group_id &&
-        animations_[i]->target_property() == event.target_property) {
-      animations_[i]->SetRunState(Animation::ABORTED, event.monotonic_time);
-      animations_[i]->set_received_finished_event(true);
-      NotifyPlayersAnimationAborted(event.monotonic_time, event.target_property,
-                                    event.group_id);
-      break;
-    }
-  }
-  switch (event.target_property) {
-    case TargetProperty::TRANSFORM:
-    case TargetProperty::OPACITY:
-    case TargetProperty::FILTER:
-      UpdateClientAnimationState(event.target_property);
-      break;
-    default:
+  DCHECK(!event.is_impl_only);
+
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->NotifyAnimationAborted(event))
       break;
   }
+
+  UpdateClientAnimationState(event.target_property);
 }
 
 void ElementAnimations::NotifyAnimationPropertyUpdate(
     const AnimationEvent& event) {
+  DCHECK(!event.is_impl_only);
   bool notify_active_elements = true;
   bool notify_pending_elements = true;
   switch (event.target_property) {
@@ -335,24 +342,23 @@ void ElementAnimations::NotifyAnimationPropertyUpdate(
 }
 
 bool ElementAnimations::HasFilterAnimationThatInflatesBounds() const {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (!animations_[i]->is_finished() &&
-        animations_[i]->target_property() == TargetProperty::FILTER &&
-        animations_[i]
-            ->curve()
-            ->ToFilterAnimationCurve()
-            ->HasFilterThatMovesPixels())
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->HasFilterAnimationThatInflatesBounds())
       return true;
   }
-
   return false;
 }
 
 bool ElementAnimations::HasTransformAnimationThatInflatesBounds() const {
-  return IsCurrentlyAnimatingProperty(TargetProperty::TRANSFORM,
-                                      ElementListType::ACTIVE) ||
-         IsCurrentlyAnimatingProperty(TargetProperty::TRANSFORM,
-                                      ElementListType::PENDING);
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->HasTransformAnimationThatInflatesBounds())
+      return true;
+  }
+  return false;
 }
 
 bool ElementAnimations::FilterAnimationBoundsForBox(const gfx::BoxF& box,
@@ -364,662 +370,119 @@ bool ElementAnimations::FilterAnimationBoundsForBox(const gfx::BoxF& box,
 bool ElementAnimations::TransformAnimationBoundsForBox(
     const gfx::BoxF& box,
     gfx::BoxF* bounds) const {
-  DCHECK(HasTransformAnimationThatInflatesBounds())
-      << "TransformAnimationBoundsForBox will give incorrect results if there "
-      << "are no transform animations affecting bounds, non-animated transform "
-      << "is not known";
-
-  // Compute bounds based on animations for which is_finished() is false.
-  // Do nothing if there are no such animations; in this case, it is assumed
-  // that callers will take care of computing bounds based on the owning layer's
-  // actual transform.
   *bounds = gfx::BoxF();
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->is_finished() ||
-        animations_[i]->target_property() != TargetProperty::TRANSFORM)
-      continue;
-
-    const TransformAnimationCurve* transform_animation_curve =
-        animations_[i]->curve()->ToTransformAnimationCurve();
-    gfx::BoxF animation_bounds;
-    bool success =
-        transform_animation_curve->AnimatedBoundsForBox(box, &animation_bounds);
+
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    gfx::BoxF player_bounds;
+    bool success = player->TransformAnimationBoundsForBox(box, &player_bounds);
     if (!success)
       return false;
-    bounds->Union(animation_bounds);
+    bounds->Union(player_bounds);
   }
-
   return true;
 }
 
 bool ElementAnimations::HasAnimationThatAffectsScale() const {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->is_finished() ||
-        animations_[i]->target_property() != TargetProperty::TRANSFORM)
-      continue;
-
-    const TransformAnimationCurve* transform_animation_curve =
-        animations_[i]->curve()->ToTransformAnimationCurve();
-    if (transform_animation_curve->AffectsScale())
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->HasAnimationThatAffectsScale())
       return true;
   }
-
   return false;
 }
 
 bool ElementAnimations::HasOnlyTranslationTransforms(
     ElementListType list_type) const {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->is_finished() ||
-        animations_[i]->target_property() != TargetProperty::TRANSFORM)
-      continue;
-
-    if ((list_type == ElementListType::ACTIVE &&
-         !animations_[i]->affects_active_elements()) ||
-        (list_type == ElementListType::PENDING &&
-         !animations_[i]->affects_pending_elements()))
-      continue;
-
-    const TransformAnimationCurve* transform_animation_curve =
-        animations_[i]->curve()->ToTransformAnimationCurve();
-    if (!transform_animation_curve->IsTranslation())
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (!player->HasOnlyTranslationTransforms(list_type))
       return false;
   }
-
   return true;
 }
 
 bool ElementAnimations::AnimationsPreserveAxisAlignment() const {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->is_finished() ||
-        animations_[i]->target_property() != TargetProperty::TRANSFORM)
-      continue;
-
-    const TransformAnimationCurve* transform_animation_curve =
-        animations_[i]->curve()->ToTransformAnimationCurve();
-    if (!transform_animation_curve->PreservesAxisAlignment())
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (!player->AnimationsPreserveAxisAlignment())
       return false;
   }
-
   return true;
 }
 
 bool ElementAnimations::AnimationStartScale(ElementListType list_type,
                                             float* start_scale) const {
   *start_scale = 0.f;
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->is_finished() ||
-        animations_[i]->target_property() != TargetProperty::TRANSFORM)
-      continue;
-
-    if ((list_type == ElementListType::ACTIVE &&
-         !animations_[i]->affects_active_elements()) ||
-        (list_type == ElementListType::PENDING &&
-         !animations_[i]->affects_pending_elements()))
-      continue;
-
-    bool forward_direction = true;
-    switch (animations_[i]->direction()) {
-      case Animation::Direction::NORMAL:
-      case Animation::Direction::ALTERNATE_NORMAL:
-        forward_direction = animations_[i]->playback_rate() >= 0.0;
-        break;
-      case Animation::Direction::REVERSE:
-      case Animation::Direction::ALTERNATE_REVERSE:
-        forward_direction = animations_[i]->playback_rate() < 0.0;
-        break;
-    }
 
-    const TransformAnimationCurve* transform_animation_curve =
-        animations_[i]->curve()->ToTransformAnimationCurve();
-    float animation_start_scale = 0.f;
-    if (!transform_animation_curve->AnimationStartScale(forward_direction,
-                                                        &animation_start_scale))
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    float player_start_scale = 0.f;
+    bool success = player->AnimationStartScale(list_type, &player_start_scale);
+    if (!success)
       return false;
-    *start_scale = std::max(*start_scale, animation_start_scale);
+    // Union: a maximum.
+    *start_scale = std::max(*start_scale, player_start_scale);
   }
+
   return true;
 }
 
 bool ElementAnimations::MaximumTargetScale(ElementListType list_type,
                                            float* max_scale) const {
   *max_scale = 0.f;
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->is_finished() ||
-        animations_[i]->target_property() != TargetProperty::TRANSFORM)
-      continue;
-
-    if ((list_type == ElementListType::ACTIVE &&
-         !animations_[i]->affects_active_elements()) ||
-        (list_type == ElementListType::PENDING &&
-         !animations_[i]->affects_pending_elements()))
-      continue;
-
-    bool forward_direction = true;
-    switch (animations_[i]->direction()) {
-      case Animation::Direction::NORMAL:
-      case Animation::Direction::ALTERNATE_NORMAL:
-        forward_direction = animations_[i]->playback_rate() >= 0.0;
-        break;
-      case Animation::Direction::REVERSE:
-      case Animation::Direction::ALTERNATE_REVERSE:
-        forward_direction = animations_[i]->playback_rate() < 0.0;
-        break;
-    }
 
-    const TransformAnimationCurve* transform_animation_curve =
-        animations_[i]->curve()->ToTransformAnimationCurve();
-    float animation_scale = 0.f;
-    if (!transform_animation_curve->MaximumTargetScale(forward_direction,
-                                                       &animation_scale))
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    float player_max_scale = 0.f;
+    bool success = player->MaximumTargetScale(list_type, &player_max_scale);
+    if (!success)
       return false;
-    *max_scale = std::max(*max_scale, animation_scale);
+    // Union: a maximum.
+    *max_scale = std::max(*max_scale, player_max_scale);
   }
 
   return true;
 }
 
-void ElementAnimations::PushNewAnimationsToImplThread(
-    ElementAnimations* element_animations_impl) const {
-  // Any new animations owned by the main thread's ElementAnimations are cloned
-  // and added to the impl thread's ElementAnimations.
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    // If the animation is already running on the impl thread, there is no
-    // need to copy it over.
-    if (element_animations_impl->GetAnimationById(animations_[i]->id()))
-      continue;
-
-    if (animations_[i]->target_property() == TargetProperty::SCROLL_OFFSET &&
-        !animations_[i]
-             ->curve()
-             ->ToScrollOffsetAnimationCurve()
-             ->HasSetInitialValue()) {
-      gfx::ScrollOffset current_scroll_offset;
-      if (element_animations_impl->has_element_in_active_list()) {
-        current_scroll_offset =
-            element_animations_impl->ScrollOffsetForAnimation();
-      } else {
-        // The owning layer isn't yet in the active tree, so the main thread
-        // scroll offset will be up to date.
-        current_scroll_offset = ScrollOffsetForAnimation();
-      }
-      animations_[i]->curve()->ToScrollOffsetAnimationCurve()->SetInitialValue(
-          current_scroll_offset);
-    }
-
-    // The new animation should be set to run as soon as possible.
-    Animation::RunState initial_run_state =
-        Animation::WAITING_FOR_TARGET_AVAILABILITY;
-    std::unique_ptr<Animation> to_add(
-        animations_[i]->CloneAndInitialize(initial_run_state));
-    DCHECK(!to_add->needs_synchronized_start_time());
-    to_add->set_affects_active_elements(false);
-    element_animations_impl->AddAnimation(std::move(to_add));
-  }
-}
-
-static bool IsCompleted(
-    Animation* animation,
-    const ElementAnimations* main_thread_element_animations) {
-  if (animation->is_impl_only()) {
-    return (animation->run_state() == Animation::WAITING_FOR_DELETION);
-  } else {
-    return !main_thread_element_animations->GetAnimationById(animation->id());
-  }
-}
-
-void ElementAnimations::RemoveAnimationsCompletedOnMainThread(
-    ElementAnimations* element_animations_impl) const {
-  bool removed_transform_animation = false;
-  bool removed_opacity_animation = false;
-  bool removed_filter_animation = false;
-  // Animations removed on the main thread should no longer affect pending
-  // elements, and should stop affecting active elements after the next call
-  // to ActivateAnimations. If already WAITING_FOR_DELETION, they can be removed
-  // immediately.
-  auto& animations = element_animations_impl->animations_;
-  for (const auto& animation : animations) {
-    if (IsCompleted(animation.get(), this)) {
-      animation->set_affects_pending_elements(false);
-      if (animation->target_property() == TargetProperty::TRANSFORM)
-        removed_transform_animation = true;
-      else if (animation->target_property() == TargetProperty::OPACITY)
-        removed_opacity_animation = true;
-      else if (animation->target_property() == TargetProperty::FILTER)
-        removed_filter_animation = true;
-    }
-  }
-  auto affects_active_only_and_is_waiting_for_deletion =
-      [](const std::unique_ptr<Animation>& animation) {
-        return animation->run_state() == Animation::WAITING_FOR_DELETION &&
-               !animation->affects_pending_elements();
-      };
-  animations.erase(
-      std::remove_if(animations.begin(), animations.end(),
-                     affects_active_only_and_is_waiting_for_deletion),
-      animations.end());
-
-  if (removed_transform_animation) {
-    element_animations_impl->UpdateClientAnimationState(
-        TargetProperty::TRANSFORM);
-  }
-  if (removed_opacity_animation) {
-    element_animations_impl->UpdateClientAnimationState(
-        TargetProperty::OPACITY);
-  }
-  if (removed_filter_animation) {
-    element_animations_impl->UpdateClientAnimationState(TargetProperty::FILTER);
-  }
-}
-
-void ElementAnimations::PushPropertiesToImplThread(
-    ElementAnimations* element_animations_impl) {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    Animation* current_impl =
-        element_animations_impl->GetAnimationById(animations_[i]->id());
-    if (current_impl)
-      animations_[i]->PushPropertiesTo(current_impl);
-  }
-  element_animations_impl->scroll_offset_animation_was_interrupted_ =
-      scroll_offset_animation_was_interrupted_;
-  scroll_offset_animation_was_interrupted_ = false;
-}
-
-void ElementAnimations::StartAnimations(base::TimeTicks monotonic_time) {
-  DCHECK(needs_to_start_animations_);
-  needs_to_start_animations_ = false;
-  // First collect running properties affecting each type of element.
-  TargetProperties blocked_properties_for_active_elements;
-  TargetProperties blocked_properties_for_pending_elements;
-  std::vector<size_t> animations_waiting_for_target;
-
-  animations_waiting_for_target.reserve(animations_.size());
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->run_state() == Animation::STARTING ||
-        animations_[i]->run_state() == Animation::RUNNING) {
-      if (animations_[i]->affects_active_elements()) {
-        blocked_properties_for_active_elements[animations_[i]
-                                                   ->target_property()] = true;
-      }
-      if (animations_[i]->affects_pending_elements()) {
-        blocked_properties_for_pending_elements[animations_[i]
-                                                    ->target_property()] = true;
-      }
-    } else if (animations_[i]->run_state() ==
-               Animation::WAITING_FOR_TARGET_AVAILABILITY) {
-      animations_waiting_for_target.push_back(i);
-    }
-  }
-
-  for (size_t i = 0; i < animations_waiting_for_target.size(); ++i) {
-    // Collect all properties for animations with the same group id (they
-    // should all also be in the list of animations).
-    size_t animation_index = animations_waiting_for_target[i];
-    Animation* animation_waiting_for_target =
-        animations_[animation_index].get();
-    // Check for the run state again even though the animation was waiting
-    // for target because it might have changed the run state while handling
-    // previous animation in this loop (if they belong to same group).
-    if (animation_waiting_for_target->run_state() ==
-        Animation::WAITING_FOR_TARGET_AVAILABILITY) {
-      TargetProperties enqueued_properties;
-      bool affects_active_elements =
-          animation_waiting_for_target->affects_active_elements();
-      bool affects_pending_elements =
-          animation_waiting_for_target->affects_pending_elements();
-      enqueued_properties[animation_waiting_for_target->target_property()] =
-          true;
-      for (size_t j = animation_index + 1; j < animations_.size(); ++j) {
-        if (animation_waiting_for_target->group() == animations_[j]->group()) {
-          enqueued_properties[animations_[j]->target_property()] = true;
-          affects_active_elements |= animations_[j]->affects_active_elements();
-          affects_pending_elements |=
-              animations_[j]->affects_pending_elements();
-        }
-      }
-
-      // Check to see if intersection of the list of properties affected by
-      // the group and the list of currently blocked properties is null, taking
-      // into account the type(s) of elements affected by the group. In any
-      // case, the group's target properties need to be added to the lists of
-      // blocked properties.
-      bool null_intersection = true;
-      static_assert(TargetProperty::FIRST_TARGET_PROPERTY == 0,
-                    "TargetProperty must be 0-based enum");
-      for (int property = TargetProperty::FIRST_TARGET_PROPERTY;
-           property <= TargetProperty::LAST_TARGET_PROPERTY; ++property) {
-        if (enqueued_properties[property]) {
-          if (affects_active_elements) {
-            if (blocked_properties_for_active_elements[property])
-              null_intersection = false;
-            else
-              blocked_properties_for_active_elements[property] = true;
-          }
-          if (affects_pending_elements) {
-            if (blocked_properties_for_pending_elements[property])
-              null_intersection = false;
-            else
-              blocked_properties_for_pending_elements[property] = true;
-          }
-        }
-      }
-
-      // If the intersection is null, then we are free to start the animations
-      // in the group.
-      if (null_intersection) {
-        animation_waiting_for_target->SetRunState(Animation::STARTING,
-                                                  monotonic_time);
-        for (size_t j = animation_index + 1; j < animations_.size(); ++j) {
-          if (animation_waiting_for_target->group() ==
-              animations_[j]->group()) {
-            animations_[j]->SetRunState(Animation::STARTING, monotonic_time);
-          }
-        }
-      } else {
-        needs_to_start_animations_ = true;
-      }
-    }
-  }
-}
-
-void ElementAnimations::PromoteStartedAnimations(base::TimeTicks monotonic_time,
-                                                 AnimationEvents* events) {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->run_state() == Animation::STARTING &&
-        animations_[i]->affects_active_elements()) {
-      animations_[i]->SetRunState(Animation::RUNNING, monotonic_time);
-      if (!animations_[i]->has_set_start_time() &&
-          !animations_[i]->needs_synchronized_start_time())
-        animations_[i]->set_start_time(monotonic_time);
-      if (events) {
-        base::TimeTicks start_time;
-        if (animations_[i]->has_set_start_time())
-          start_time = animations_[i]->start_time();
-        else
-          start_time = monotonic_time;
-        AnimationEvent started_event(
-            AnimationEvent::STARTED, element_id_, animations_[i]->group(),
-            animations_[i]->target_property(), start_time);
-        started_event.is_impl_only = animations_[i]->is_impl_only();
-        if (started_event.is_impl_only)
-          NotifyAnimationStarted(started_event);
-        else
-          events->events_.push_back(started_event);
-      }
-    }
-  }
-}
+void ElementAnimations::SetNeedsUpdateImplClientState(bool transform,
+                                                      bool opacity,
+                                                      bool filter) {
+  if (transform)
+    needs_update_impl_client_state_transform_ = true;
+  if (opacity)
+    needs_update_impl_client_state_opacity_ = true;
+  if (filter)
+    needs_update_impl_client_state_filter_ = true;
 
-void ElementAnimations::MarkFinishedAnimations(base::TimeTicks monotonic_time) {
-  bool finished_transform_animation = false;
-  bool finished_opacity_animation = false;
-  bool finished_filter_animation = false;
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (!animations_[i]->is_finished() &&
-        animations_[i]->IsFinishedAt(monotonic_time)) {
-      animations_[i]->SetRunState(Animation::FINISHED, monotonic_time);
-      if (animations_[i]->target_property() == TargetProperty::TRANSFORM)
-        finished_transform_animation = true;
-      else if (animations_[i]->target_property() == TargetProperty::OPACITY)
-        finished_opacity_animation = true;
-      else if (animations_[i]->target_property() == TargetProperty::FILTER)
-        finished_filter_animation = true;
-    }
-  }
-  if (finished_transform_animation)
-    UpdateClientAnimationState(TargetProperty::TRANSFORM);
-  if (finished_opacity_animation)
-    UpdateClientAnimationState(TargetProperty::OPACITY);
-  if (finished_filter_animation)
-    UpdateClientAnimationState(TargetProperty::FILTER);
+  if (needs_update_impl_client_state_transform_ ||
+      needs_update_impl_client_state_opacity_ ||
+      needs_update_impl_client_state_filter_)
+    SetNeedsPushProperties();
 }
 
-void ElementAnimations::MarkAnimationsForDeletion(
-    base::TimeTicks monotonic_time,
-    AnimationEvents* events) {
-  bool marked_animations_for_deletions = false;
-  std::vector<size_t> animations_with_same_group_id;
-
-  animations_with_same_group_id.reserve(animations_.size());
-  // Non-aborted animations are marked for deletion after a corresponding
-  // AnimationEvent::FINISHED event is sent or received. This means that if
-  // we don't have an events vector, we must ensure that non-aborted animations
-  // have received a finished event before marking them for deletion.
-  for (size_t i = 0; i < animations_.size(); i++) {
-    int group_id = animations_[i]->group();
-    if (animations_[i]->run_state() == Animation::ABORTED) {
-      if (events && !animations_[i]->is_impl_only()) {
-        AnimationEvent aborted_event(
-            AnimationEvent::ABORTED, element_id_, group_id,
-            animations_[i]->target_property(), monotonic_time);
-        events->events_.push_back(aborted_event);
-      }
-      // If on the compositor or on the main thread and received finish event,
-      // animation can be marked for deletion.
-      if (events || animations_[i]->received_finished_event()) {
-        animations_[i]->SetRunState(Animation::WAITING_FOR_DELETION,
-                                    monotonic_time);
-        marked_animations_for_deletions = true;
-      }
-      continue;
-    }
-
-    // If running on the compositor and need to complete an aborted animation
-    // on the main thread.
-    if (events &&
-        animations_[i]->run_state() ==
-            Animation::ABORTED_BUT_NEEDS_COMPLETION) {
-      AnimationEvent aborted_event(AnimationEvent::TAKEOVER, element_id_,
-                                   group_id, animations_[i]->target_property(),
-                                   monotonic_time);
-      aborted_event.animation_start_time =
-          (animations_[i]->start_time() - base::TimeTicks()).InSecondsF();
-      const ScrollOffsetAnimationCurve* scroll_offset_animation_curve =
-          animations_[i]->curve()->ToScrollOffsetAnimationCurve();
-      aborted_event.curve = scroll_offset_animation_curve->Clone();
-      // Notify the compositor that the animation is finished.
-      NotifyPlayersAnimationFinished(aborted_event.monotonic_time,
-                                     aborted_event.target_property,
-                                     aborted_event.group_id);
-      // Notify main thread.
-      events->events_.push_back(aborted_event);
-
-      // Remove the animation from the compositor.
-      animations_[i]->SetRunState(Animation::WAITING_FOR_DELETION,
-                                  monotonic_time);
-      marked_animations_for_deletions = true;
-      continue;
-    }
-
-    bool all_anims_with_same_id_are_finished = false;
-
-    // Since deleting an animation on the main thread leads to its deletion
-    // on the impl thread, we only mark a FINISHED main thread animation for
-    // deletion once it has received a FINISHED event from the impl thread.
-    bool animation_i_will_send_or_has_received_finish_event =
-        animations_[i]->is_controlling_instance() ||
-        animations_[i]->is_impl_only() ||
-        animations_[i]->received_finished_event();
-    // If an animation is finished, and not already marked for deletion,
-    // find out if all other animations in the same group are also finished.
-    if (animations_[i]->run_state() == Animation::FINISHED &&
-        animation_i_will_send_or_has_received_finish_event) {
-      // Clear the animations_with_same_group_id if it was added for
-      // the previous animation's iteration.
-      if (animations_with_same_group_id.size() > 0)
-        animations_with_same_group_id.clear();
-      all_anims_with_same_id_are_finished = true;
-      for (size_t j = 0; j < animations_.size(); ++j) {
-        bool animation_j_will_send_or_has_received_finish_event =
-            animations_[j]->is_controlling_instance() ||
-            animations_[j]->is_impl_only() ||
-            animations_[j]->received_finished_event();
-        if (group_id == animations_[j]->group()) {
-          if (!animations_[j]->is_finished() ||
-              (animations_[j]->run_state() == Animation::FINISHED &&
-               !animation_j_will_send_or_has_received_finish_event)) {
-            all_anims_with_same_id_are_finished = false;
-            break;
-          } else if (j >= i &&
-                     animations_[j]->run_state() != Animation::ABORTED) {
-            // Mark down the animations which belong to the same group
-            // and is not yet aborted. If this current iteration finds that all
-            // animations with same ID are finished, then the marked
-            // animations below will be set to WAITING_FOR_DELETION in next
-            // iteration.
-            animations_with_same_group_id.push_back(j);
-          }
-        }
-      }
-    }
-    if (all_anims_with_same_id_are_finished) {
-      // We now need to remove all animations with the same group id as
-      // group_id (and send along animation finished notifications, if
-      // necessary).
-      for (size_t j = 0; j < animations_with_same_group_id.size(); j++) {
-        size_t animation_index = animations_with_same_group_id[j];
-        if (events) {
-          AnimationEvent finished_event(
-              AnimationEvent::FINISHED, element_id_,
-              animations_[animation_index]->group(),
-              animations_[animation_index]->target_property(), monotonic_time);
-          finished_event.is_impl_only =
-              animations_[animation_index]->is_impl_only();
-          if (finished_event.is_impl_only)
-            NotifyAnimationFinished(finished_event);
-          else
-            events->events_.push_back(finished_event);
-        }
-        animations_[animation_index]->SetRunState(
-            Animation::WAITING_FOR_DELETION, monotonic_time);
-      }
-      marked_animations_for_deletions = true;
-    }
-  }
-  if (marked_animations_for_deletions)
-    NotifyPlayersAnimationWaitingForDeletion();
+void ElementAnimations::ClearNeedsUpdateImplClientState() {
+  needs_update_impl_client_state_transform_ = false;
+  needs_update_impl_client_state_opacity_ = false;
+  needs_update_impl_client_state_filter_ = false;
 }
 
-void ElementAnimations::MarkAbortedAnimationsForDeletion(
-    ElementAnimations* element_animations_impl) const {
-  bool aborted_transform_animation = false;
-  bool aborted_opacity_animation = false;
-  bool aborted_filter_animation = false;
-  auto& animations_impl = element_animations_impl->animations_;
-  for (const auto& animation_impl : animations_impl) {
-    // If the animation has been aborted on the main thread, mark it for
-    // deletion.
-    if (Animation* animation = GetAnimationById(animation_impl->id())) {
-      if (animation->run_state() == Animation::ABORTED) {
-        animation_impl->SetRunState(Animation::WAITING_FOR_DELETION,
-                                    element_animations_impl->last_tick_time_);
-        animation->SetRunState(Animation::WAITING_FOR_DELETION,
-                               last_tick_time_);
-        if (animation_impl->target_property() == TargetProperty::TRANSFORM)
-          aborted_transform_animation = true;
-        else if (animation_impl->target_property() == TargetProperty::OPACITY)
-          aborted_opacity_animation = true;
-        else if (animation_impl->target_property() == TargetProperty::FILTER)
-          aborted_filter_animation = true;
-      }
-    }
-  }
-
-  if (aborted_transform_animation) {
-    element_animations_impl->UpdateClientAnimationState(
-        TargetProperty::TRANSFORM);
-  }
-  if (aborted_opacity_animation) {
-    element_animations_impl->UpdateClientAnimationState(
-        TargetProperty::OPACITY);
-  }
-  if (aborted_filter_animation) {
-    element_animations_impl->UpdateClientAnimationState(TargetProperty::FILTER);
-  }
-}
-
-void ElementAnimations::PurgeAnimationsMarkedForDeletion() {
-  animations_.erase(
-      std::remove_if(animations_.begin(), animations_.end(),
-                     [](const std::unique_ptr<Animation>& animation) {
-                       return animation->run_state() ==
-                              Animation::WAITING_FOR_DELETION;
-                     }),
-      animations_.end());
-}
-
-void ElementAnimations::TickAnimations(base::TimeTicks monotonic_time) {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->run_state() == Animation::STARTING ||
-        animations_[i]->run_state() == Animation::RUNNING ||
-        animations_[i]->run_state() == Animation::PAUSED) {
-      if (!animations_[i]->InEffect(monotonic_time))
-        continue;
-
-      base::TimeDelta trimmed =
-          animations_[i]->TrimTimeToCurrentIteration(monotonic_time);
-
-      switch (animations_[i]->target_property()) {
-        case TargetProperty::TRANSFORM: {
-          const TransformAnimationCurve* transform_animation_curve =
-              animations_[i]->curve()->ToTransformAnimationCurve();
-          const gfx::Transform transform =
-              transform_animation_curve->GetValue(trimmed);
-          NotifyClientTransformAnimated(
-              transform, animations_[i]->affects_active_elements(),
-              animations_[i]->affects_pending_elements());
-          break;
-        }
-
-        case TargetProperty::OPACITY: {
-          const FloatAnimationCurve* float_animation_curve =
-              animations_[i]->curve()->ToFloatAnimationCurve();
-          const float opacity = std::max(
-              std::min(float_animation_curve->GetValue(trimmed), 1.0f), 0.f);
-          NotifyClientOpacityAnimated(
-              opacity, animations_[i]->affects_active_elements(),
-              animations_[i]->affects_pending_elements());
-          break;
-        }
-
-        case TargetProperty::FILTER: {
-          const FilterAnimationCurve* filter_animation_curve =
-              animations_[i]->curve()->ToFilterAnimationCurve();
-          const FilterOperations filter =
-              filter_animation_curve->GetValue(trimmed);
-          NotifyClientFilterAnimated(
-              filter, animations_[i]->affects_active_elements(),
-              animations_[i]->affects_pending_elements());
-          break;
-        }
-
-        case TargetProperty::BACKGROUND_COLOR: {
-          // Not yet implemented.
-          break;
-        }
-
-        case TargetProperty::SCROLL_OFFSET: {
-          const ScrollOffsetAnimationCurve* scroll_offset_animation_curve =
-              animations_[i]->curve()->ToScrollOffsetAnimationCurve();
-          const gfx::ScrollOffset scroll_offset =
-              scroll_offset_animation_curve->GetValue(trimmed);
-          NotifyClientScrollOffsetAnimated(
-              scroll_offset, animations_[i]->affects_active_elements(),
-              animations_[i]->affects_pending_elements());
-          break;
-        }
-      }
-    }
-  }
-}
-
-void ElementAnimations::UpdateActivation(UpdateActivationType type) {
-  bool force = type == FORCE_ACTIVATION;
+void ElementAnimations::UpdateActivation(ActivationType type) {
+  bool force = type == ActivationType::FORCE;
   if (animation_host_) {
     bool was_active = is_active_;
     is_active_ = false;
-    for (size_t i = 0; i < animations_.size(); ++i) {
-      if (animations_[i]->run_state() != Animation::WAITING_FOR_DELETION) {
+
+    ElementAnimations::PlayersList::Iterator it(players_list_.get());
+    AnimationPlayer* player;
+    while ((player = it.GetNext()) != nullptr) {
+      if (player->HasNonDeletedAnimation()) {
         is_active_ = true;
         break;
       }
@@ -1036,6 +499,10 @@ void ElementAnimations::UpdateActivation(UpdateActivationType type) {
   }
 }
 
+void ElementAnimations::UpdateActivationNormal() {
+  UpdateActivation(ActivationType::NORMAL);
+}
+
 void ElementAnimations::NotifyClientOpacityAnimated(
     float opacity,
     bool notify_active_elements,
@@ -1126,7 +593,7 @@ void ElementAnimations::NotifyClientAnimationChanged(
   }
 }
 
-void ElementAnimations::UpdateClientAnimationState(
+void ElementAnimations::UpdateClientAnimationStateInternal(
     TargetProperty::Type property) {
   struct PropertyAnimationState* animation_state = nullptr;
   switch (property) {
@@ -1158,18 +625,23 @@ void ElementAnimations::UpdateClientAnimationState(
   DCHECK(was_potentially_animating_for_pending_elements ||
          !was_currently_running_animation_for_pending_elements);
 
-  for (const auto& animation : animations_) {
-    if (!animation->is_finished() && animation->target_property() == property) {
-      animation_state->potentially_animating_for_active_elements |=
-          animation->affects_active_elements();
-      animation_state->potentially_animating_for_pending_elements |=
-          animation->affects_pending_elements();
-      animation_state->currently_running_for_active_elements =
-          animation_state->potentially_animating_for_active_elements &&
-          animation->InEffect(last_tick_time_);
-      animation_state->currently_running_for_pending_elements =
-          animation_state->potentially_animating_for_pending_elements &&
-          animation->InEffect(last_tick_time_);
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    for (const auto& animation : player->animations()) {
+      if (!animation->is_finished() &&
+          animation->target_property() == property) {
+        animation_state->potentially_animating_for_active_elements |=
+            animation->affects_active_elements();
+        animation_state->potentially_animating_for_pending_elements |=
+            animation->affects_pending_elements();
+        animation_state->currently_running_for_active_elements =
+            animation_state->potentially_animating_for_active_elements &&
+            animation->InEffect(last_tick_time_);
+        animation_state->currently_running_for_pending_elements =
+            animation_state->potentially_animating_for_pending_elements &&
+            animation->InEffect(last_tick_time_);
+      }
     }
   }
 
@@ -1203,169 +675,116 @@ void ElementAnimations::UpdateClientAnimationState(
 }
 
 bool ElementAnimations::HasActiveAnimation() const {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (!animations_[i]->is_finished())
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->HasActiveAnimation())
       return true;
   }
+
   return false;
 }
 
 bool ElementAnimations::HasAnyAnimation() const {
-  return !animations_.empty();
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->has_any_animation())
+      return true;
+  }
+
+  return false;
 }
 
 bool ElementAnimations::IsPotentiallyAnimatingProperty(
     TargetProperty::Type target_property,
     ElementListType list_type) const {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (!animations_[i]->is_finished() &&
-        animations_[i]->target_property() == target_property) {
-      if ((list_type == ElementListType::ACTIVE &&
-           animations_[i]->affects_active_elements()) ||
-          (list_type == ElementListType::PENDING &&
-           animations_[i]->affects_pending_elements()))
-        return true;
-    }
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->IsPotentiallyAnimatingProperty(target_property, list_type))
+      return true;
   }
+
   return false;
 }
 
 bool ElementAnimations::IsCurrentlyAnimatingProperty(
     TargetProperty::Type target_property,
     ElementListType list_type) const {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (!animations_[i]->is_finished() &&
-        animations_[i]->InEffect(last_tick_time_) &&
-        animations_[i]->target_property() == target_property) {
-      if ((list_type == ElementListType::ACTIVE &&
-           animations_[i]->affects_active_elements()) ||
-          (list_type == ElementListType::PENDING &&
-           animations_[i]->affects_pending_elements()))
-        return true;
-    }
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->IsCurrentlyAnimatingProperty(target_property, list_type))
+      return true;
   }
+
   return false;
 }
 
-void ElementAnimations::PauseAnimation(int animation_id,
-                                       base::TimeDelta time_offset) {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->id() == animation_id) {
-      animations_[i]->SetRunState(Animation::PAUSED,
-                                  time_offset + animations_[i]->start_time() +
-                                      animations_[i]->time_offset());
-    }
-  }
-  SetNeedsPushProperties();
+void ElementAnimations::SetScrollOffsetAnimationWasInterrupted() {
+  scroll_offset_animation_was_interrupted_ = true;
 }
 
-void ElementAnimations::RemoveAnimation(int animation_id) {
-  bool removed_transform_animation = false;
-  bool removed_opacity_animation = false;
-  bool removed_filter_animation = false;
-  // Since we want to use the animations that we're going to remove, we need to
-  // use a stable_parition here instead of remove_if. Remove_if leaves the
-  // removed items in an unspecified state.
-  auto animations_to_remove = std::stable_partition(
-      animations_.begin(), animations_.end(),
-      [animation_id](const std::unique_ptr<Animation>& animation) {
-        return animation->id() != animation_id;
-      });
-  for (auto it = animations_to_remove; it != animations_.end(); ++it) {
-    if ((*it)->target_property() == TargetProperty::SCROLL_OFFSET) {
-      scroll_offset_animation_was_interrupted_ = true;
-    } else if ((*it)->target_property() == TargetProperty::TRANSFORM &&
-               !(*it)->is_finished()) {
-      removed_transform_animation = true;
-    } else if ((*it)->target_property() == TargetProperty::OPACITY &&
-               !(*it)->is_finished()) {
-      removed_opacity_animation = true;
-    } else if ((*it)->target_property() == TargetProperty::FILTER &&
-               !(*it)->is_finished()) {
-      removed_filter_animation = true;
-    }
+bool ElementAnimations::needs_to_start_animations_for_testing() const {
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (player->needs_to_start_animations())
+      return true;
   }
 
-  animations_.erase(animations_to_remove, animations_.end());
-  UpdateActivation(NORMAL_ACTIVATION);
-  if (removed_transform_animation)
-    UpdateClientAnimationState(TargetProperty::TRANSFORM);
-  if (removed_opacity_animation)
-    UpdateClientAnimationState(TargetProperty::OPACITY);
-  if (removed_filter_animation)
-    UpdateClientAnimationState(TargetProperty::FILTER);
+  return false;
+}
 
-  SetNeedsPushProperties();
+void ElementAnimations::PauseAnimation(int animation_id,
+                                       base::TimeDelta time_offset) {
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr)
+    player->PauseAnimation(animation_id, time_offset.InSecondsF());
 }
 
-void ElementAnimations::AbortAnimation(int animation_id) {
-  if (Animation* animation = GetAnimationById(animation_id)) {
-    if (!animation->is_finished()) {
-      animation->SetRunState(Animation::ABORTED, last_tick_time_);
-      switch (animation->target_property()) {
-        case TargetProperty::TRANSFORM:
-        case TargetProperty::OPACITY:
-        case TargetProperty::FILTER:
-          UpdateClientAnimationState(animation->target_property());
-          break;
-        default:
-          break;
-      }
-    }
-  }
+void ElementAnimations::RemoveAnimation(int animation_id) {
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr)
+    player->RemoveAnimation(animation_id);
+}
 
-  SetNeedsPushProperties();
+void ElementAnimations::AbortAnimation(int animation_id) {
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr)
+    player->AbortAnimation(animation_id);
 }
 
 void ElementAnimations::AbortAnimations(TargetProperty::Type target_property,
                                         bool needs_completion) {
-  if (needs_completion)
-    DCHECK(target_property == TargetProperty::SCROLL_OFFSET);
-
-  bool aborted_animation = false;
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    if (animations_[i]->target_property() == target_property &&
-        !animations_[i]->is_finished()) {
-      // Currently only impl-only scroll offset animations can be completed on
-      // the main thread.
-      if (needs_completion && animations_[i]->is_impl_only()) {
-        animations_[i]->SetRunState(Animation::ABORTED_BUT_NEEDS_COMPLETION,
-                                    last_tick_time_);
-      } else {
-        animations_[i]->SetRunState(Animation::ABORTED, last_tick_time_);
-      }
-      aborted_animation = true;
-    }
-  }
-  if (aborted_animation) {
-    switch (target_property) {
-      case TargetProperty::TRANSFORM:
-      case TargetProperty::OPACITY:
-      case TargetProperty::FILTER:
-        UpdateClientAnimationState(target_property);
-        break;
-      default:
-        break;
-    }
-  }
-
-  SetNeedsPushProperties();
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr)
+    player->AbortAnimations(target_property, needs_completion);
 }
 
 Animation* ElementAnimations::GetAnimation(
     TargetProperty::Type target_property) const {
-  for (size_t i = 0; i < animations_.size(); ++i) {
-    size_t index = animations_.size() - i - 1;
-    if (animations_[index]->target_property() == target_property)
-      return animations_[index].get();
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (Animation* animation = player->GetAnimation(target_property))
+      return animation;
   }
   return nullptr;
 }
 
 Animation* ElementAnimations::GetAnimationById(int animation_id) const {
-  for (size_t i = 0; i < animations_.size(); ++i)
-    if (animations_[i]->id() == animation_id)
-      return animations_[i].get();
+  ElementAnimations::PlayersList::Iterator it(players_list_.get());
+  AnimationPlayer* player;
+  while ((player = it.GetNext()) != nullptr) {
+    if (Animation* animation = player->GetAnimationById(animation_id))
+      return animation;
+  }
   return nullptr;
 }
 
@@ -1440,61 +859,6 @@ void ElementAnimations::IsAnimatingChanged(ElementListType list_type,
   }
 }
 
-void ElementAnimations::NotifyPlayersAnimationStarted(
-    base::TimeTicks monotonic_time,
-    TargetProperty::Type target_property,
-    int group) {
-  ElementAnimations::PlayersList::Iterator it(players_list_.get());
-  AnimationPlayer* player;
-  // TODO(crbug.com/634916): Shouldn't manually iterate through the list if
-  // base::ObserverList has a callback mechanism.
-  while ((player = it.GetNext()) != nullptr)
-    player->NotifyAnimationStarted(monotonic_time, target_property, group);
-}
-
-void ElementAnimations::NotifyPlayersAnimationFinished(
-    base::TimeTicks monotonic_time,
-    TargetProperty::Type target_property,
-    int group) {
-  ElementAnimations::PlayersList::Iterator it(players_list_.get());
-  AnimationPlayer* player;
-  while ((player = it.GetNext()) != nullptr)
-    player->NotifyAnimationFinished(monotonic_time, target_property, group);
-}
-
-void ElementAnimations::NotifyPlayersAnimationAborted(
-    base::TimeTicks monotonic_time,
-    TargetProperty::Type target_property,
-    int group) {
-  ElementAnimations::PlayersList::Iterator it(players_list_.get());
-  AnimationPlayer* player;
-  while ((player = it.GetNext()) != nullptr)
-    player->NotifyAnimationAborted(monotonic_time, target_property, group);
-}
-
-void ElementAnimations::NotifyPlayersAnimationWaitingForDeletion() {
-  ElementAnimations::PlayersList::Iterator it(players_list_.get());
-  AnimationPlayer* player;
-  while ((player = it.GetNext()) != nullptr)
-    player->NotifyAnimationWaitingForDeletion();
-}
-
-void ElementAnimations::NotifyPlayersAnimationTakeover(
-    base::TimeTicks monotonic_time,
-    TargetProperty::Type target_property,
-    double animation_start_time,
-    std::unique_ptr<AnimationCurve> curve) {
-  DCHECK(curve);
-  ElementAnimations::PlayersList::Iterator it(players_list_.get());
-  AnimationPlayer* player;
-  while ((player = it.GetNext()) != nullptr) {
-    std::unique_ptr<AnimationCurve> animation_curve = curve->Clone();
-    player->NotifyAnimationTakeover(monotonic_time, target_property,
-                                    animation_start_time,
-                                    std::move(animation_curve));
-  }
-}
-
 gfx::ScrollOffset ElementAnimations::ScrollOffsetForAnimation() const {
   if (animation_host()) {
     DCHECK(animation_host()->mutator_host_client());