CC Animations: Make LayerAnimationController creation optional

cc/layers/layer.cc

 // Copyright 2010 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 "cc/layers/layer.h"
 
 #include <algorithm>
 
 #include "base/atomic_sequence_num.h"
 #include "base/location.h"
@@ skipping 65 matching lines @@
       scroll_blocks_on_(SCROLL_BLOCKS_ON_NONE),
       background_color_(0),
       opacity_(1.f),
       blend_mode_(SkXfermode::kSrcOver_Mode),
       scroll_parent_(nullptr),
       clip_parent_(nullptr),
       replica_layer_(nullptr),
       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);
 }
 
 Layer::~Layer() {
   // Our parent should be holding a reference to us so there should be no
   // way for us to be destroyed while we still have a parent.
   DCHECK(!parent());
   // Similarly we shouldn't have a layer tree host since it also keeps a
   // 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();
 
   // Remove the parent reference from all children and dependents.
   RemoveAllChildren();
   if (mask_layer_.get()) {
     DCHECK_EQ(this, mask_layer_->parent());
     mask_layer_->RemoveFromParent();
   }
@@ skipping 18 matching lines @@
 
   for (size_t i = 0; i < children_.size(); ++i)
     children_[i]->SetLayerTreeHost(host);
 
   if (mask_layer_.get())
     mask_layer_->SetLayerTreeHost(host);
   if (replica_layer_.get())
     replica_layer_->SetLayerTreeHost(host);
 
   if (host) {
-    layer_animation_controller_->SetAnimationRegistrar(
-        host->animation_registrar());
-
+    RegisterForAnimations(host->animation_registrar(), host->settings());
     if (host->settings().layer_transforms_should_scale_layer_contents)
       reset_raster_scale_to_unknown();
   }
 
   if (host && layer_animation_controller_->has_any_animation())
     host->SetNeedsCommit();
 }
 
 void Layer::SetNeedsUpdate() {
   if (layer_tree_host_ && !ignore_set_needs_commit_)
@@ skipping 1191 matching lines @@
 void Layer::OnAnimationWaitingForDeletion() {
   // Animations are only deleted during PushProperties.
   SetNeedsPushProperties();
 }
 
 bool Layer::IsActive() const {
   return true;
 }
 
 bool Layer::AddAnimation(scoped_ptr <Animation> animation) {
-  if (!layer_animation_controller_->animation_registrar())
+  if (!layer_animation_controller_ ||
+      !layer_animation_controller_->animation_registrar())
     return false;
 
   if (animation->target_property() == Animation::SCROLL_OFFSET &&
       !layer_animation_controller_->animation_registrar()
            ->supports_scroll_animations())
     return false;
 
   UMA_HISTOGRAM_BOOLEAN("Renderer.AnimationAddedToOrphanLayer",
                         !layer_tree_host_);
   layer_animation_controller_->AddAnimation(animation.Pass());
@@ skipping 23 matching lines @@
   layer_animation_controller_->RemoveValueObserver(this);
   layer_animation_controller_ = controller;
   layer_animation_controller_->AddValueObserver(this);
   SetNeedsCommit();
 }
 
 bool Layer::HasActiveAnimation() const {
   return layer_animation_controller_->HasActiveAnimation();
 }
 
+void Layer::RegisterForAnimations(AnimationRegistrar* registrar,
+                                  const LayerTreeSettings& settings) {
+  if (!layer_animation_controller_) {
+    layer_animation_controller_ = LayerAnimationController::Create(layer_id_);
+    layer_animation_controller_->AddValueObserver(this);
+    layer_animation_controller_->set_value_provider(this);
+  }
+
+  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);
 }
 
 SimpleEnclosedRegion Layer::VisibleContentOpaqueRegion() const {
   if (contents_opaque())
     return SimpleEnclosedRegion(visible_content_rect());
   return SimpleEnclosedRegion();
 }
 
 ScrollbarLayerInterface* Layer::ToScrollbarLayer() {
@@ skipping 54 matching lines @@
 
 void Layer::DidBeginTracing() {
   // We'll be dumping layer trees as part of trace, so make sure
   // PushPropertiesTo() propagates layer debug info to the impl
   // side -- otherwise this won't happen for the the layers that
   // remain unchanged since tracing started.
   SetNeedsPushProperties();
 }
 
 }  // namespace cc