CC Animations: Make LayerAnimationController creation optional

Don't call SetAnimationRegistrar directly - make RegisterForAnimations explicit.

Previous episodes:
https://codereview.chromium.org/1122393003/
https://codereview.chromium.org/1159633002/

This is a prerequisite to implement compositor animation timelines. Next episode:
https://codereview.chromium.org/947033002/

BUG=394777
R=ajuma@chromium.org
R=vollick@chromium.org
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1101823002

Cr-Commit-Position: refs/heads/master@{#331739}

4 files changed, 28 insertions, 10 deletions

diff --git a/cc/blink/web_layer_impl.cc b/cc/blink/web_layer_impl.cc
index bfe4616..f0fd873 100644
--- a/cc/blink/web_layer_impl.cc
+++ b/cc/blink/web_layer_impl.cc
@@ -65,7 +65,8 @@ WebLayerImpl::WebLayerImpl(scoped_refptr<Layer> layer) : layer_(layer) {
 
 WebLayerImpl::~WebLayerImpl() {
   layer_->ClearRenderSurface();
-  layer_->set_layer_animation_delegate(nullptr);
+  if (animation_delegate_adapter_.get())
+    layer_->set_layer_animation_delegate(nullptr);
   web_layer_client_ = nullptr;
 }
 
diff --git a/cc/layers/layer.cc b/cc/layers/layer.cc
index c449c89..d795670 100644
--- a/cc/layers/layer.cc
+++ b/cc/layers/layer.cc
@@ -90,9 +90,11 @@ Layer::Layer(const LayerSettings& settings)
       raster_scale_(0.f),
       client_(nullptr),
       frame_timing_requests_dirty_(false) {
-  layer_animation_controller_ = LayerAnimationController::Create(layer_id_);
-  layer_animation_controller_->AddValueObserver(this);
-  layer_animation_controller_->set_value_provider(this);
+  if (!settings.use_compositor_animation_timelines) {
+    layer_animation_controller_ = LayerAnimationController::Create(layer_id_);
+    layer_animation_controller_->AddValueObserver(this);
+    layer_animation_controller_->set_value_provider(this);
+  }
 }
 
 Layer::~Layer() {
@@ -103,8 +105,10 @@ Layer::~Layer() {
   // reference to us.
   DCHECK(!layer_tree_host());
 
-  layer_animation_controller_->RemoveValueObserver(this);
-  layer_animation_controller_->remove_value_provider(this);
+  if (layer_animation_controller_) {
+    layer_animation_controller_->RemoveValueObserver(this);
+    layer_animation_controller_->remove_value_provider(this);
+  }
 
   RemoveFromScrollTree();
   RemoveFromClipTree();
@@ -143,9 +147,7 @@ void Layer::SetLayerTreeHost(LayerTreeHost* host) {
     replica_layer_->SetLayerTreeHost(host);
 
   if (host) {
-    layer_animation_controller_->SetAnimationRegistrar(
-        host->animation_registrar());
-
+    RegisterForAnimations(host->animation_registrar());
     if (host->settings().layer_transforms_should_scale_layer_contents)
       reset_raster_scale_to_unknown();
   }
@@ -1477,6 +1479,7 @@ bool Layer::IsActive() const {
 }
 
 bool Layer::AddAnimation(scoped_ptr <Animation> animation) {
+  DCHECK(layer_animation_controller_);
   if (!layer_animation_controller_->animation_registrar())
     return false;
 
@@ -1493,18 +1496,21 @@ bool Layer::AddAnimation(scoped_ptr <Animation> animation) {
 }
 
 void Layer::PauseAnimation(int animation_id, double time_offset) {
+  DCHECK(layer_animation_controller_);
   layer_animation_controller_->PauseAnimation(
       animation_id, base::TimeDelta::FromSecondsD(time_offset));
   SetNeedsCommit();
 }
 
 void Layer::RemoveAnimation(int animation_id) {
+  DCHECK(layer_animation_controller_);
   layer_animation_controller_->RemoveAnimation(animation_id);
   SetNeedsCommit();
 }
 
 void Layer::RemoveAnimation(int animation_id,
                             Animation::TargetProperty property) {
+  DCHECK(layer_animation_controller_);
   layer_animation_controller_->RemoveAnimation(animation_id, property);
   SetNeedsCommit();
 }
@@ -1518,16 +1524,24 @@ void Layer::SetLayerAnimationControllerForTest(
 }
 
 bool Layer::HasActiveAnimation() const {
+  DCHECK(layer_animation_controller_);
   return layer_animation_controller_->HasActiveAnimation();
 }
 
+void Layer::RegisterForAnimations(AnimationRegistrar* registrar) {
+  if (layer_animation_controller_)
+    layer_animation_controller_->SetAnimationRegistrar(registrar);
+}
+
 void Layer::AddLayerAnimationEventObserver(
     LayerAnimationEventObserver* animation_observer) {
+  DCHECK(layer_animation_controller_);
   layer_animation_controller_->AddEventObserver(animation_observer);
 }
 
 void Layer::RemoveLayerAnimationEventObserver(
     LayerAnimationEventObserver* animation_observer) {
+  DCHECK(layer_animation_controller_);
   layer_animation_controller_->RemoveEventObserver(animation_observer);
 }
 
diff --git a/cc/layers/layer.h b/cc/layers/layer.h
index 6a44ae9..89cdc6d 100644
--- a/cc/layers/layer.h
+++ b/cc/layers/layer.h
@@ -62,6 +62,7 @@ class LayerSettings;
 class LayerTreeHost;
 class LayerTreeHostCommon;
 class LayerTreeImpl;
+class LayerTreeSettings;
 class PriorityCalculator;
 class RenderingStatsInstrumentation;
 class ResourceUpdateQueue;
@@ -425,10 +426,12 @@ class CC_EXPORT Layer : public base::RefCounted<Layer>,
       scoped_refptr<LayerAnimationController> controller);
 
   void set_layer_animation_delegate(AnimationDelegate* delegate) {
+    DCHECK(layer_animation_controller_);
     layer_animation_controller_->set_layer_animation_delegate(delegate);
   }
 
   bool HasActiveAnimation() const;
+  void RegisterForAnimations(AnimationRegistrar* registrar);
 
   void AddLayerAnimationEventObserver(
       LayerAnimationEventObserver* animation_observer);
diff --git a/cc/layers/layer_unittest.cc b/cc/layers/layer_unittest.cc
index 16893a1..61d9333 100644
--- a/cc/layers/layer_unittest.cc
+++ b/cc/layers/layer_unittest.cc
@@ -1173,7 +1173,7 @@ TEST_F(LayerLayerTreeHostTest, ShouldNotAddAnimationWithoutAnimationRegistrar) {
   EXPECT_FALSE(AddTestAnimation(layer.get()));
 
   scoped_ptr<AnimationRegistrar> registrar = AnimationRegistrar::Create();
-  layer->layer_animation_controller()->SetAnimationRegistrar(registrar.get());
+  layer->RegisterForAnimations(registrar.get());
 
   // Case 2: with an AnimationRegistrar, the animation should be accepted.
   EXPECT_TRUE(AddTestAnimation(layer.get()));