compositor: Tick the UI animations from cc, instead of from timer callbacks.

ui/compositor/layer.cc

Index: ui/compositor/layer.cc
diff --git a/ui/compositor/layer.cc b/ui/compositor/layer.cc
index ca3ff288ee293a43b49d39bee0f6f97311e6a0cd..d3585595473c887cf9e8a4487f2415ec7e92407b 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -142,10 +142,15 @@ void Layer::SetCompositor(Compositor* compositor) {
   DCHECK(!compositor || !compositor_);
   DCHECK(!compositor || compositor->root_layer() == this);
   DCHECK(!parent_);
+  if (compositor_) {
+    RemoveAnimatorsInTreeFromCollection(
+        compositor_->layer_animator_collection());
+  }
   compositor_ = compositor;
   if (compositor) {
     OnDeviceScaleFactorChanged(compositor->device_scale_factor());
     SendPendingThreadedAnimations();
+    AddAnimatorsInTreeToCollection(compositor_->layer_animator_collection());
   }
 }
 
@@ -159,15 +164,20 @@ void Layer::Add(Layer* child) {
   child->OnDeviceScaleFactorChanged(device_scale_factor_);
   if (GetCompositor())
     child->SendPendingThreadedAnimations();
+  LayerAnimatorCollection* collection = GetLayerAnimatorCollection();
+  if (collection)
+    child->AddAnimatorsInTreeToCollection(collection);
 }
 
 void Layer::Remove(Layer* child) {
+  LayerAnimatorCollection* collection = GetLayerAnimatorCollection();
+  if (collection)
+    child->RemoveAnimatorsInTreeFromCollection(collection);

[ajuma, 2014/06/02 14:53:22]

This should be moved to after the StopAnimatingProperty call below (which might
otherwise cause us to get re-added to the collection, since it could lead to
other animations starting).

[sadrul, 2014/06/02 17:53:44]

Done.

   // Current bounds are used to calculate offsets when layers are reparented.
   // Stop (and complete) an ongoing animation to update the bounds immediately.
-  if (child->GetAnimator()) {
-    child->GetAnimator()->StopAnimatingProperty(
-        ui::LayerAnimationElement::BOUNDS);
-  }
+  LayerAnimator* child_animator = child->animator_;
+  if (child_animator)
+    child_animator->StopAnimatingProperty(ui::LayerAnimationElement::BOUNDS);
   std::vector<Layer*>::iterator i =
       std::find(children_.begin(), children_.end(), child);
   DCHECK(i != children_.end());
@@ -873,6 +883,11 @@ void Layer::RemoveThreadedAnimation(int animation_id) {
       pending_threaded_animations_.end());
 }
 
+LayerAnimatorCollection* Layer::GetLayerAnimatorCollection() {
+  Compositor* compositor = GetCompositor();
+  return compositor ? compositor->layer_animator_collection() : NULL;
+}
+
 void Layer::SendPendingThreadedAnimations() {
   for (cc::ScopedPtrVector<cc::Animation>::iterator it =
            pending_threaded_animations_.begin();
@@ -930,4 +945,32 @@ void Layer::RecomputePosition() {
   cc_layer_->SetPosition(gfx::PointF(bounds_.x(), bounds_.y()));
 }
 
+void Layer::AddAnimatorsInTreeToCollection(
+    LayerAnimatorCollection* collection) {
+  DCHECK(collection);
+  if (IsAnimating())
+    collection->StartAnimator(animator_.get());

[ajuma, 2014/06/02 14:53:22]

LayerAnimator::is_started_ will have a stale value if we directly Start/Stop
from Layer. How about calling into LayerAnimator and asking it to Add/Remove
itself from the collection? (As long as we Remove before disconnecting the layer
from the tree, and Add after re-adding the layer to a tree, I think the
collection that LayerAnimator gets from its delegate should be the same as the
one we'd use here.)

[sadrul, 2014/06/02 17:53:44]

Done.

+  std::for_each(
+      children_.begin(),
+      children_.end(),
+      std::bind2nd(std::mem_fun(&Layer::AddAnimatorsInTreeToCollection),
+                   collection));
+}
+
+void Layer::RemoveAnimatorsInTreeFromCollection(
+    LayerAnimatorCollection* collection) {
+  DCHECK(collection);
+  if (IsAnimating())
+    collection->StopAnimator(animator_.get());
+  std::for_each(
+      children_.begin(),
+      children_.end(),
+      std::bind2nd(std::mem_fun(&Layer::RemoveAnimatorsInTreeFromCollection),
+                   collection));
+}
+
+bool Layer::IsAnimating() const {
+  return animator_ && animator_->is_animating();
+}
+
 }  // namespace ui