CC Animations: Redirect all compositor animation requests to AnimationHost.

cc/trees/layer_tree_host_unittest_animation_timelines.cc

Index: cc/trees/layer_tree_host_unittest_animation_timelines.cc
diff --git a/cc/trees/layer_tree_host_unittest_animation_timelines.cc b/cc/trees/layer_tree_host_unittest_animation_timelines.cc
index b3b4a6e799985c54e54428317e6f153e6d40030e..353840d05e18bf72bf183e8eeebbd805ac3768dd 100644
--- a/cc/trees/layer_tree_host_unittest_animation_timelines.cc
+++ b/cc/trees/layer_tree_host_unittest_animation_timelines.cc
@@ -5,6 +5,9 @@
 #include "cc/trees/layer_tree_host.h"
 
 #include "cc/animation/animation_curve.h"
+#include "cc/animation/animation_host.h"
+#include "cc/animation/animation_player.h"
+#include "cc/animation/animation_timeline.h"
 #include "cc/animation/layer_animation_controller.h"
 #include "cc/animation/scroll_offset_animation_curve.h"
 #include "cc/animation/timing_function.h"
@@ -18,5 +21,723 @@
 #include "cc/trees/layer_tree_impl.h"
 
 namespace cc {
-namespace {}  // namespace
+namespace {
+
+class LayerTreeHostTimelinesTest : public LayerTreeTest {
+ public:
+  LayerTreeHostTimelinesTest()
+      : timeline_id_(1), player_id_(2), player_child_id_(3) {
+    timeline_ = AnimationTimeline::Create(timeline_id_);
+    player_ = AnimationPlayer::Create(player_id_);
+    player_child_ = AnimationPlayer::Create(player_child_id_);
+
+    player_->set_layer_animation_delegate(this);
+  }
+
+  void InitializeSettings(LayerTreeSettings* settings) override {
+    settings->use_compositor_animation_timelines = true;
+  }
+
+  void SetupTree() override { LayerTreeTest::SetupTree(); }
+
+  void AttachPlayersToTimeline() {
+    layer_tree_host()->animation_host()->AddAnimationTimeline(timeline_.get());
+    timeline_->AttachPlayer(player_.get());
+    timeline_->AttachPlayer(player_child_.get());
+  }
+
+ protected:
+  scoped_refptr<AnimationTimeline> timeline_;
+  scoped_refptr<AnimationPlayer> player_;
+  scoped_refptr<AnimationPlayer> player_child_;
+
+  const int timeline_id_;
+  const int player_id_;
+  const int player_child_id_;
+};
+
+// Add a layer animation and confirm that
+// LayerTreeHostImpl::UpdateAnimationState does get called.
+// Evolved frome LayerTreeHostAnimationTestAddAnimation
+class LayerTreeHostTimelinesTestAddAnimation
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestAddAnimation()
+      : update_animation_state_was_called_(false) {}
+
+  void BeginTest() override {
+    AttachPlayersToTimeline();
+    player_->AttachLayer(layer_tree_host()->root_layer()->id());
+    PostAddInstantAnimationToMainThreadPlayer(player_.get());
+  }
+
+  void UpdateAnimationState(LayerTreeHostImpl* host_impl,
+                            bool has_unfinished_animation) override {
+    EXPECT_FALSE(has_unfinished_animation);
+    update_animation_state_was_called_ = true;
+  }
+
+  void NotifyAnimationStarted(base::TimeTicks monotonic_time,
+                              Animation::TargetProperty target_property,
+                              int group) override {
+    EXPECT_LT(base::TimeTicks(), monotonic_time);
+
+    LayerAnimationController* controller =
+        player_->layer_animation_controller();
+    Animation* animation = controller->GetAnimation(Animation::OPACITY);
+    if (animation)
+      player_->RemoveAnimation(animation->id());
+
+    EndTest();
+  }
+
+  void AfterTest() override { EXPECT_TRUE(update_animation_state_was_called_); }
+
+ private:
+  bool update_animation_state_was_called_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostTimelinesTestAddAnimation);
+
+// Add a layer animation to a layer, but continually fail to draw. Confirm that
+// after a while, we do eventually force a draw.
+// Evolved from LayerTreeHostAnimationTestCheckerboardDoesNotStarveDraws.
+class LayerTreeHostTimelinesTestCheckerboardDoesNotStarveDraws
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestCheckerboardDoesNotStarveDraws()
+      : started_animating_(false) {}
+
+  void BeginTest() override {
+    AttachPlayersToTimeline();
+    player_->AttachLayer(layer_tree_host()->root_layer()->id());
+    PostAddAnimationToMainThreadPlayer(player_.get());
+  }
+
+  void AnimateLayers(LayerTreeHostImpl* host_impl,
+                     base::TimeTicks monotonic_time) override {
+    started_animating_ = true;
+  }
+
+  void DrawLayersOnThread(LayerTreeHostImpl* host_impl) override {
+    if (started_animating_)
+      EndTest();
+  }
+
+  DrawResult PrepareToDrawOnThread(LayerTreeHostImpl* host_impl,
+                                   LayerTreeHostImpl::FrameData* frame,
+                                   DrawResult draw_result) override {
+    return DRAW_ABORTED_CHECKERBOARD_ANIMATIONS;
+  }
+
+  void AfterTest() override {}
+
+ private:
+  bool started_animating_;
+};
+
+// Starvation can only be an issue with the MT compositor.
+MULTI_THREAD_TEST_F(LayerTreeHostTimelinesTestCheckerboardDoesNotStarveDraws);
+
+// Ensures that animations eventually get deleted.
+// Evolved from LayerTreeHostAnimationTestAnimationsGetDeleted.
+class LayerTreeHostTimelinesTestAnimationsGetDeleted
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestAnimationsGetDeleted()
+      : started_animating_(false) {}
+
+  void BeginTest() override {
+    AttachPlayersToTimeline();
+    player_->AttachLayer(layer_tree_host()->root_layer()->id());
+    PostAddAnimationToMainThreadPlayer(player_.get());
+  }
+
+  void AnimateLayers(LayerTreeHostImpl* host_impl,
+                     base::TimeTicks monotonic_time) override {
+    bool have_animations = !host_impl->animation_host()
+                                ->animation_registrar()
+                                ->active_animation_controllers_for_testing()
+                                .empty();
+    if (!started_animating_ && have_animations) {
+      started_animating_ = true;
+      return;
+    }
+
+    if (started_animating_ && !have_animations)
+      EndTest();
+  }
+
+  void NotifyAnimationFinished(base::TimeTicks monotonic_time,
+                               Animation::TargetProperty target_property,
+                               int group) override {
+    // Animations on the impl-side controller only get deleted during a commit,
+    // so we need to schedule a commit.
+    layer_tree_host()->SetNeedsCommit();
+  }
+
+  void AfterTest() override {}
+
+ private:
+  bool started_animating_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostTimelinesTestAnimationsGetDeleted);
+
+// Ensure that an animation's timing function is respected.
+// Evolved from LayerTreeHostAnimationTestAddAnimationWithTimingFunction.
+class LayerTreeHostTimelinesTestAddAnimationWithTimingFunction
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestAddAnimationWithTimingFunction() {}
+
+  void SetupTree() override {
+    LayerTreeHostTimelinesTest::SetupTree();
+    content_ = FakeContentLayer::Create(&client_);
+    content_->SetBounds(gfx::Size(4, 4));
+    layer_tree_host()->root_layer()->AddChild(content_);
+
+    AttachPlayersToTimeline();
+    player_child_->AttachLayer(content_->id());
+  }
+
+  void BeginTest() override {
+    PostAddAnimationToMainThreadPlayer(player_child_.get());
+  }
+
+  void AnimateLayers(LayerTreeHostImpl* host_impl,
+                     base::TimeTicks monotonic_time) override {
+    scoped_refptr<AnimationTimeline> timeline_impl =
+        host_impl->animation_host()->GetTimelineById(timeline_id_);
+    scoped_refptr<AnimationPlayer> player_child_impl =
+        timeline_impl->GetPlayerById(player_child_id_);
+
+    LayerAnimationController* controller_impl =
+        player_child_impl->layer_animation_controller();
+    if (!controller_impl)
+      return;
+
+    Animation* animation = controller_impl->GetAnimation(Animation::OPACITY);
+    if (!animation)
+      return;
+
+    const FloatAnimationCurve* curve =
+        animation->curve()->ToFloatAnimationCurve();
+    float start_opacity = curve->GetValue(base::TimeDelta());
+    float end_opacity = curve->GetValue(curve->Duration());
+    float linearly_interpolated_opacity =
+        0.25f * end_opacity + 0.75f * start_opacity;
+    base::TimeDelta time = TimeUtil::Scale(curve->Duration(), 0.25f);
+    // If the linear timing function associated with this animation was not
+    // picked up, then the linearly interpolated opacity would be different
+    // because of the default ease timing function.
+    EXPECT_FLOAT_EQ(linearly_interpolated_opacity, curve->GetValue(time));
+
+    EndTest();
+  }
+
+  void AfterTest() override {}
+
+  FakeContentLayerClient client_;
+  scoped_refptr<FakeContentLayer> content_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(
+    LayerTreeHostTimelinesTestAddAnimationWithTimingFunction);
+
+// Ensures that main thread animations have their start times synchronized with
+// impl thread animations.
+// Evolved from LayerTreeHostAnimationTestSynchronizeAnimationStartTimes.
+class LayerTreeHostTimelinesTestSynchronizeAnimationStartTimes
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestSynchronizeAnimationStartTimes() {}
+
+  void SetupTree() override {
+    LayerTreeHostTimelinesTest::SetupTree();
+    content_ = FakeContentLayer::Create(&client_);
+    content_->SetBounds(gfx::Size(4, 4));
+
+    layer_tree_host()->root_layer()->AddChild(content_);
+
+    AttachPlayersToTimeline();
+    player_child_->set_layer_animation_delegate(this);
+    player_child_->AttachLayer(content_->id());
+  }
+
+  void BeginTest() override {
+    PostAddAnimationToMainThreadPlayer(player_child_.get());
+  }
+
+  void NotifyAnimationStarted(base::TimeTicks monotonic_time,
+                              Animation::TargetProperty target_property,
+                              int group) override {
+    LayerAnimationController* controller =
+        player_child_->layer_animation_controller();
+    Animation* animation = controller->GetAnimation(Animation::OPACITY);
+    main_start_time_ = animation->start_time();
+    controller->RemoveAnimation(animation->id());
+    EndTest();
+  }
+
+  void UpdateAnimationState(LayerTreeHostImpl* impl_host,
+                            bool has_unfinished_animation) override {
+    scoped_refptr<AnimationTimeline> timeline_impl =
+        impl_host->animation_host()->GetTimelineById(timeline_id_);
+    scoped_refptr<AnimationPlayer> player_child_impl =
+        timeline_impl->GetPlayerById(player_child_id_);
+
+    LayerAnimationController* controller =
+        player_child_impl->layer_animation_controller();
+    Animation* animation = controller->GetAnimation(Animation::OPACITY);
+    if (!animation)
+      return;
+
+    impl_start_time_ = animation->start_time();
+  }
+
+  void AfterTest() override {
+    EXPECT_EQ(impl_start_time_, main_start_time_);
+    EXPECT_LT(base::TimeTicks(), impl_start_time_);
+  }
+
+ private:
+  base::TimeTicks main_start_time_;
+  base::TimeTicks impl_start_time_;
+  FakeContentLayerClient client_;
+  scoped_refptr<FakeContentLayer> content_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(
+    LayerTreeHostTimelinesTestSynchronizeAnimationStartTimes);
+
+// Ensures that notify animation finished is called.
+// Evolved from LayerTreeHostAnimationTestAnimationFinishedEvents.
+class LayerTreeHostTimelinesTestAnimationFinishedEvents
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestAnimationFinishedEvents() {}
+
+  void BeginTest() override {
+    AttachPlayersToTimeline();
+    player_->AttachLayer(layer_tree_host()->root_layer()->id());
+    PostAddInstantAnimationToMainThreadPlayer(player_.get());
+  }
+
+  void NotifyAnimationFinished(base::TimeTicks monotonic_time,
+                               Animation::TargetProperty target_property,
+                               int group) override {
+    LayerAnimationController* controller =
+        player_->layer_animation_controller();
+    Animation* animation = controller->GetAnimation(Animation::OPACITY);
+    if (animation)
+      controller->RemoveAnimation(animation->id());
+    EndTest();
+  }
+
+  void AfterTest() override {}
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(
+    LayerTreeHostTimelinesTestAnimationFinishedEvents);
+
+// Ensures that when opacity is being animated, this value does not cause the
+// subtree to be skipped.
+// Evolved from LayerTreeHostAnimationTestDoNotSkipLayersWithAnimatedOpacity.
+class LayerTreeHostTimelinesTestDoNotSkipLayersWithAnimatedOpacity
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestDoNotSkipLayersWithAnimatedOpacity()
+      : update_check_layer_(FakeContentLayer::Create(&client_)) {}
+
+  void SetupTree() override {
+    update_check_layer_->SetOpacity(0.f);
+    layer_tree_host()->SetRootLayer(update_check_layer_);
+    LayerTreeHostTimelinesTest::SetupTree();
+
+    AttachPlayersToTimeline();
+    player_->AttachLayer(update_check_layer_->id());
+  }
+
+  void BeginTest() override {
+    PostAddAnimationToMainThreadPlayer(player_.get());
+  }
+
+  void DidActivateTreeOnThread(LayerTreeHostImpl* host_impl) override {
+    scoped_refptr<AnimationTimeline> timeline_impl =
+        host_impl->animation_host()->GetTimelineById(timeline_id_);
+    scoped_refptr<AnimationPlayer> player_impl =
+        timeline_impl->GetPlayerById(player_id_);
+
+    LayerAnimationController* controller_impl =
+        player_impl->layer_animation_controller();
+    Animation* animation_impl =
+        controller_impl->GetAnimation(Animation::OPACITY);
+    controller_impl->RemoveAnimation(animation_impl->id());
+    EndTest();
+  }
+
+  void AfterTest() override {
+    // Update() should have been called once, proving that the layer was not
+    // skipped.
+    EXPECT_EQ(1u, update_check_layer_->update_count());
+
+    // clear update_check_layer_ so LayerTreeHost dies.
+    update_check_layer_ = NULL;
+  }
+
+ private:
+  FakeContentLayerClient client_;
+  scoped_refptr<FakeContentLayer> update_check_layer_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(
+    LayerTreeHostTimelinesTestDoNotSkipLayersWithAnimatedOpacity);
+
+// Layers added to tree with existing active animations should have the
+// animation correctly recognized.
+// Evolved from LayerTreeHostAnimationTestLayerAddedWithAnimation.
+class LayerTreeHostTimelinesTestLayerAddedWithAnimation
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestLayerAddedWithAnimation() {}
+
+  void BeginTest() override { PostSetNeedsCommitToMainThread(); }
+
+  void DidCommit() override {
+    if (layer_tree_host()->source_frame_number() == 1) {
+      AttachPlayersToTimeline();
+
+      scoped_refptr<Layer> layer = Layer::Create();
+      player_->AttachLayer(layer->id());
+      player_->set_layer_animation_delegate(this);
+
+      // Any valid AnimationCurve will do here.
+      scoped_ptr<AnimationCurve> curve(new FakeFloatAnimationCurve());
+      scoped_ptr<Animation> animation(
+          Animation::Create(curve.Pass(), 1, 1, Animation::OPACITY));
+      player_->AddAnimation(animation.Pass());
+
+      // We add the animation *before* attaching the layer to the tree.
+      layer_tree_host()->root_layer()->AddChild(layer);
+    }
+  }
+
+  void AnimateLayers(LayerTreeHostImpl* impl_host,
+                     base::TimeTicks monotonic_time) override {
+    EndTest();
+  }
+
+  void AfterTest() override {}
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(
+    LayerTreeHostTimelinesTestLayerAddedWithAnimation);
+
+// Make sure the main thread can still execute animations when CanDraw() is not
+// true.
+// Evolved from LayerTreeHostAnimationTestRunAnimationWhenNotCanDraw
+class LayerTreeHostTimelinesTestRunAnimationWhenNotCanDraw
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestRunAnimationWhenNotCanDraw() : started_times_(0) {}
+
+  void SetupTree() override {
+    LayerTreeHostTimelinesTest::SetupTree();
+    content_ = FakeContentLayer::Create(&client_);
+    content_->SetBounds(gfx::Size(4, 4));
+    layer_tree_host()->root_layer()->AddChild(content_);
+
+    AttachPlayersToTimeline();
+    player_child_->AttachLayer(content_->id());
+    player_child_->set_layer_animation_delegate(this);
+  }
+
+  void BeginTest() override {
+    layer_tree_host()->SetViewportSize(gfx::Size());
+    PostAddAnimationToMainThreadPlayer(player_child_.get());
+  }
+
+  void NotifyAnimationStarted(base::TimeTicks monotonic_time,
+                              Animation::TargetProperty target_property,
+                              int group) override {
+    started_times_++;
+  }
+
+  void NotifyAnimationFinished(base::TimeTicks monotonic_time,
+                               Animation::TargetProperty target_property,
+                               int group) override {
+    EndTest();
+  }
+
+  void AfterTest() override { EXPECT_EQ(1, started_times_); }
+
+ private:
+  int started_times_;
+  FakeContentLayerClient client_;
+  scoped_refptr<FakeContentLayer> content_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(
+    LayerTreeHostTimelinesTestRunAnimationWhenNotCanDraw);
+
+// Animations should not be started when frames are being skipped due to
+// checkerboard.
+// Evolved from LayerTreeHostAnimationTestCheckerboardDoesntStartAnimations.
+class LayerTreeHostTimelinesTestCheckerboardDoesntStartAnimations
+    : public LayerTreeHostTimelinesTest {
+  void SetupTree() override {
+    LayerTreeHostTimelinesTest::SetupTree();
+    content_ = FakeContentLayer::Create(&client_);
+    content_->SetBounds(gfx::Size(4, 4));
+    layer_tree_host()->root_layer()->AddChild(content_);
+
+    AttachPlayersToTimeline();
+    player_child_->AttachLayer(content_->id());
+    player_child_->set_layer_animation_delegate(this);
+  }
+
+  void InitializeSettings(LayerTreeSettings* settings) override {
+    // Make sure that drawing many times doesn't cause a checkerboarded
+    // animation to start so we avoid flake in this test.
+    settings->timeout_and_draw_when_animation_checkerboards = false;
+    LayerTreeHostTimelinesTest::InitializeSettings(settings);
+  }
+
+  void BeginTest() override {
+    prevented_draw_ = 0;
+    added_animations_ = 0;
+    started_times_ = 0;
+
+    PostSetNeedsCommitToMainThread();
+  }
+
+  DrawResult PrepareToDrawOnThread(LayerTreeHostImpl* host_impl,
+                                   LayerTreeHostImpl::FrameData* frame_data,
+                                   DrawResult draw_result) override {
+    if (added_animations_ < 2)
+      return draw_result;
+    if (TestEnded())
+      return draw_result;
+    // Act like there is checkerboard when the second animation wants to draw.
+    ++prevented_draw_;
+    if (prevented_draw_ > 2)
+      EndTest();
+    return DRAW_ABORTED_CHECKERBOARD_ANIMATIONS;
+  }
+
+  void DidCommitAndDrawFrame() override {
+    switch (layer_tree_host()->source_frame_number()) {
+      case 1:
+        // The animation is longer than 1 BeginFrame interval.
+        AddOpacityTransitionToPlayer(player_child_.get(), 0.1, 0.2f, 0.8f,
+                                     false);
+        added_animations_++;
+        break;
+      case 2:
+        // This second animation will not be drawn so it should not start.
+        AddAnimatedTransformToPlayer(player_child_.get(), 0.1, 5, 5);
+        added_animations_++;
+        break;
+    }
+  }
+
+  void NotifyAnimationStarted(base::TimeTicks monotonic_time,
+                              Animation::TargetProperty target_property,
+                              int group) override {
+    if (TestEnded())
+      return;
+    started_times_++;
+  }
+
+  void AfterTest() override {
+    // Make sure we tried to draw the second animation but failed.
+    EXPECT_LT(0, prevented_draw_);
+    // The first animation should be started, but the second should not because
+    // of checkerboard.
+    EXPECT_EQ(1, started_times_);
+  }
+
+  int prevented_draw_;
+  int added_animations_;
+  int started_times_;
+  FakeContentLayerClient client_;
+  scoped_refptr<FakeContentLayer> content_;
+};
+
+MULTI_THREAD_TEST_F(
+    LayerTreeHostTimelinesTestCheckerboardDoesntStartAnimations);
+
+// When animations are simultaneously added to an existing layer and to a new
+// layer, they should start at the same time, even when there's already a
+// running animation on the existing layer.
+// Evolved from LayerTreeHostAnimationTestAnimationsAddedToNewAndExistingLayers.
+class LayerTreeHostTimelinesTestAnimationsAddedToNewAndExistingLayers
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestAnimationsAddedToNewAndExistingLayers()
+      : frame_count_with_pending_tree_(0) {}
+
+  void BeginTest() override {
+    AttachPlayersToTimeline();
+    PostSetNeedsCommitToMainThread();
+  }
+
+  void DidCommit() override {
+    if (layer_tree_host()->source_frame_number() == 1) {
+      player_->AttachLayer(layer_tree_host()->root_layer()->id());
+      AddAnimatedTransformToPlayer(player_.get(), 4, 1, 1);
+    } else if (layer_tree_host()->source_frame_number() == 2) {
+      AddOpacityTransitionToPlayer(player_.get(), 1, 0.f, 0.5f, true);
+
+      scoped_refptr<Layer> layer = Layer::Create();
+      layer_tree_host()->root_layer()->AddChild(layer);
+      layer->set_layer_animation_delegate(this);
+      layer->SetBounds(gfx::Size(4, 4));
+
+      player_child_->AttachLayer(layer->id());
+      AddOpacityTransitionToPlayer(player_child_.get(), 1, 0.f, 0.5f, true);
+    }
+  }
+
+  void BeginCommitOnThread(LayerTreeHostImpl* host_impl) override {
+    if (host_impl->settings().impl_side_painting)
+      host_impl->BlockNotifyReadyToActivateForTesting(true);
+  }
+
+  void CommitCompleteOnThread(LayerTreeHostImpl* host_impl) override {
+    // For the commit that added animations to new and existing layers, keep
+    // blocking activation. We want to verify that even with activation blocked,
+    // the animation on the layer that's already in the active tree won't get a
+    // head start.
+    if (host_impl->settings().impl_side_painting &&
+        host_impl->pending_tree()->source_frame_number() != 2) {
+      host_impl->BlockNotifyReadyToActivateForTesting(false);
+    }
+  }
+
+  void WillBeginImplFrameOnThread(LayerTreeHostImpl* host_impl,
+                                  const BeginFrameArgs& args) override {
+    if (!host_impl->pending_tree() ||
+        host_impl->pending_tree()->source_frame_number() != 2)
+      return;
+
+    frame_count_with_pending_tree_++;
+    if (frame_count_with_pending_tree_ == 2 &&
+        host_impl->settings().impl_side_painting) {
+      host_impl->BlockNotifyReadyToActivateForTesting(false);
+    }
+  }
+
+  void UpdateAnimationState(LayerTreeHostImpl* host_impl,
+                            bool has_unfinished_animation) override {
+    scoped_refptr<AnimationTimeline> timeline_impl =
+        host_impl->animation_host()->GetTimelineById(timeline_id_);
+    scoped_refptr<AnimationPlayer> player_impl =
+        timeline_impl->GetPlayerById(player_id_);
+    scoped_refptr<AnimationPlayer> player_child_impl =
+        timeline_impl->GetPlayerById(player_child_id_);
+
+    // wait for tree activation.
+    if (!player_impl->layer_animation_controller())
+      return;
+
+    LayerAnimationController* root_controller_impl =
+        player_impl->layer_animation_controller();
+    Animation* root_animation =
+        root_controller_impl->GetAnimation(Animation::OPACITY);
+    if (!root_animation || root_animation->run_state() != Animation::RUNNING)
+      return;
+
+    LayerAnimationController* child_controller_impl =
+        player_child_impl->layer_animation_controller();
+    Animation* child_animation =
+        child_controller_impl->GetAnimation(Animation::OPACITY);
+    EXPECT_EQ(Animation::RUNNING, child_animation->run_state());
+    EXPECT_EQ(root_animation->start_time(), child_animation->start_time());
+    root_controller_impl->AbortAnimations(Animation::OPACITY);
+    root_controller_impl->AbortAnimations(Animation::TRANSFORM);
+    child_controller_impl->AbortAnimations(Animation::OPACITY);
+    EndTest();
+  }
+
+  void AfterTest() override {}
+
+ private:
+  int frame_count_with_pending_tree_;
+};
+
+SINGLE_AND_MULTI_THREAD_BLOCKNOTIFY_TEST_F(
+    LayerTreeHostTimelinesTestAnimationsAddedToNewAndExistingLayers);
+
+// Evolved from LayerTreeHostAnimationTestAddAnimationAfterAnimating.
+class LayerTreeHostTimelinesTestAddAnimationAfterAnimating
+    : public LayerTreeHostTimelinesTest {
+ public:
+  LayerTreeHostTimelinesTestAddAnimationAfterAnimating()
+      : num_swap_buffers_(0) {}
+
+  void SetupTree() override {
+    LayerTreeHostTimelinesTest::SetupTree();
+    content_ = Layer::Create();
+    content_->SetBounds(gfx::Size(4, 4));
+    layer_tree_host()->root_layer()->AddChild(content_);
+
+    AttachPlayersToTimeline();
+
+    player_->AttachLayer(layer_tree_host()->root_layer()->id());
+    player_child_->AttachLayer(content_->id());
+  }
+
+  void BeginTest() override { PostSetNeedsCommitToMainThread(); }
+
+  void DidCommit() override {
+    switch (layer_tree_host()->source_frame_number()) {
+      case 1:
+        // First frame: add an animation to the root layer.
+        AddAnimatedTransformToPlayer(player_.get(), 0.1, 5, 5);
+        break;
+      case 2:
+        // Second frame: add an animation to the content layer. The root layer
+        // animation has caused us to animate already during this frame.
+        AddOpacityTransitionToPlayer(player_child_.get(), 0.1, 5, 5, false);
+        break;
+    }
+  }
+
+  void SwapBuffersOnThread(LayerTreeHostImpl* host_impl, bool result) override {
+    // After both animations have started, verify that they have valid
+    // start times.
+    num_swap_buffers_++;
+    AnimationRegistrar::AnimationControllerMap controllers_copy =
+        host_impl->animation_host()
+            ->animation_registrar()
+            ->active_animation_controllers_for_testing();
+    if (controllers_copy.size() == 2u) {
+      EndTest();
+      EXPECT_GE(num_swap_buffers_, 3);
+      for (auto& it : controllers_copy) {
+        int id = it.first;
+        if (id == host_impl->RootLayer()->id()) {
+          Animation* anim = it.second->GetAnimation(Animation::TRANSFORM);
+          EXPECT_GT((anim->start_time() - base::TimeTicks()).InSecondsF(), 0);
+        } else if (id == host_impl->RootLayer()->children()[0]->id()) {
+          Animation* anim = it.second->GetAnimation(Animation::OPACITY);
+          EXPECT_GT((anim->start_time() - base::TimeTicks()).InSecondsF(), 0);
+        }
+      }
+    }
+  }
+
+  void AfterTest() override {}
+
+ private:
+  scoped_refptr<Layer> content_;
+  int num_swap_buffers_;
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(
+    LayerTreeHostTimelinesTestAddAnimationAfterAnimating);
+
+}  // namespace
 }  // namespace cc