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

ui/compositor/layer.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/compositor/layer.h"
 
 #include <algorithm>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 141 matching lines @@
 void Layer::Add(Layer* child) {
   DCHECK(!child->compositor_);
   if (child->parent_)
     child->parent_->Remove(child);
   child->parent_ = this;
   children_.push_back(child);
   cc_layer_->AddChild(child->cc_layer_);
   child->OnDeviceScaleFactorChanged(device_scale_factor_);
   if (GetCompositor())
     child->SendPendingThreadedAnimations();
+  if (child->GetAnimator() && child->GetAnimator()->is_animating()) {

[piman, 2014/05/23 21:38:56]

nit: GetAnimator() is non-trivial:
1- can we call it once and keep the return value?
2- it also has a side effect of creating the animator. Doesn't that mean we'll
create a LayerAnimator for every layer, even though it may never be animated?

Actually, GetAnimator() says that it never returns NULL.

[sadrul, 2014/05/23 21:56:11]

Done. Added Layer::IsAnimating() const { return animator_ &&
animator_->is_animating(); } and using that instead (here, and also in
Layer::Remove()).

+    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);
+    if (child->GetAnimator()->is_animating()) {
+      LayerAnimatorCollection* collection = GetLayerAnimatorCollection();
+      if (collection)
+        collection->StopAnimator(child->GetAnimator());
+    }
   }
   std::vector<Layer*>::iterator i =
       std::find(children_.begin(), children_.end(), child);
   DCHECK(i != children_.end());
   children_.erase(i);
   child->parent_ = NULL;
   child->cc_layer_->RemoveFromParent();
 }
 
 void Layer::StackAtTop(Layer* child) {
@@ skipping 687 matching lines @@
   }
 
   pending_threaded_animations_.erase(
       cc::remove_if(&pending_threaded_animations_,
                     pending_threaded_animations_.begin(),
                     pending_threaded_animations_.end(),
                     HasAnimationId(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();
        it != pending_threaded_animations_.end();
        ++it)
     cc_layer_->AddAnimation(pending_threaded_animations_.take(it));
 
   pending_threaded_animations_.clear();
 
   for (size_t i = 0; i < children_.size(); ++i)
@@ skipping 38 matching lines @@
     delegated_renderer_layer_->SetDisplaySize(frame_size_in_dip_);
   }
   cc_layer_->SetBounds(size);
 }
 
 void Layer::RecomputePosition() {
   cc_layer_->SetPosition(gfx::PointF(bounds_.x(), bounds_.y()));
 }
 
 }  // namespace ui