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 cfa02f27f7e64d399f7af7e887b17c1ed8e21037..ee9b12ecd5f2ab331a8f9df9d462b5bca8b4656e 100644
--- a/ui/compositor/layer.cc
+++ b/ui/compositor/layer.cc
@@ -159,14 +159,24 @@ void Layer::Add(Layer* child) {
   child->OnDeviceScaleFactorChanged(device_scale_factor_);
   if (GetCompositor())
     child->SendPendingThreadedAnimations();
+  if (child->IsAnimating()) {
+    LayerAnimatorCollection* collection = GetLayerAnimatorCollection();
+    if (collection)
+      collection->StartAnimator(child->GetAnimator());
+  }
 }
 
 void Layer::Remove(Layer* child) {
   // 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);
+    if (child->IsAnimating()) {
+      LayerAnimatorCollection* collection = GetLayerAnimatorCollection();
+      if (collection)
+        collection->StopAnimator(child_animator);
+    }
   }
   std::vector<Layer*>::iterator i =
       std::find(children_.begin(), children_.end(), child);
@@ -874,6 +884,11 @@ 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();
@@ -931,4 +946,8 @@ void Layer::RecomputePosition() {
   cc_layer_->SetPosition(gfx::PointF(bounds_.x(), bounds_.y()));
 }
 
+bool Layer::IsAnimating() const {
+  return animator_ && animator_->is_animating();
+}
+
 }  // namespace ui