Reland of cc : Make LayerImpl destruction independent of tree hierarchy

cc/layers/layer_impl.cc

Index: cc/layers/layer_impl.cc
diff --git a/cc/layers/layer_impl.cc b/cc/layers/layer_impl.cc
index 407449d774176c40a69ec524808bbb5d3ea21e35..ed6218de99cdf095edb19e5cbd1a1767c9513e73 100644
--- a/cc/layers/layer_impl.cc
+++ b/cc/layers/layer_impl.cc
@@ -104,11 +104,12 @@
   TRACE_EVENT_OBJECT_DELETED_WITH_ID(
       TRACE_DISABLED_BY_DEFAULT("cc.debug"), "cc::LayerImpl", this);
 
+  // The mask and replica layers should have been removed already.
   if (mask_layer_)
-    layer_tree_impl_->RemoveLayer(mask_layer_id_);
+    DCHECK(!layer_tree_impl_->RemoveLayer(mask_layer_id_));
   if (replica_layer_)
-    layer_tree_impl_->RemoveLayer(replica_layer_id_);
-  ClearChildList();
+    DCHECK(!layer_tree_impl_->RemoveLayer(replica_layer_id_));
+  children_.clear();
 }
 
 void LayerImpl::AddChild(std::unique_ptr<LayerImpl> child) {
@@ -128,14 +129,6 @@
 
 void LayerImpl::SetParent(LayerImpl* parent) {
   parent_ = parent;
-}
-
-void LayerImpl::ClearChildList() {
-  if (children_.empty())
-    return;
-  for (auto* child : children_)
-    layer_tree_impl_->RemoveLayer(child->id());
-  children_.clear();
 }
 
 void LayerImpl::ClearLinksToOtherLayers() {
@@ -848,11 +841,14 @@
   replica_layer_id_ = new_layer_id;
 }
 
-std::unique_ptr<LayerImpl> LayerImpl::TakeReplicaLayer() {
+std::unique_ptr<LayerImpl> LayerImpl::TakeReplicaLayerForTesting() {
   replica_layer_id_ = -1;
   std::unique_ptr<LayerImpl> ret;
-  if (replica_layer_)
+  if (replica_layer_) {
+    if (replica_layer_->mask_layer())
+      replica_layer_->SetMaskLayer(nullptr);
     ret = layer_tree_impl_->RemoveLayer(replica_layer_->id());
+  }
   replica_layer_ = nullptr;
   return ret;
 }