Fix assignedNodes({flatten:true}) to return fallback content in document tree

third_party/WebKit/Source/core/html/HTMLSlotElement.cpp

Index: third_party/WebKit/Source/core/html/HTMLSlotElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLSlotElement.cpp b/third_party/WebKit/Source/core/html/HTMLSlotElement.cpp
index 12eec94cb5b617d39bc22179f0aaa73672cff0c4..7140661b46caba76b940adb952768b76d59e0d15 100644
--- a/third_party/WebKit/Source/core/html/HTMLSlotElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLSlotElement.cpp
@@ -77,10 +77,14 @@ const HeapVector<Member<Node>> HTMLSlotElement::assignedNodesForBinding(
 const HeapVector<Member<Node>>
 HTMLSlotElement::GetDistributedNodesForBinding() {
   DCHECK(!NeedsDistributionRecalc());
+  return GetDistributedNodesWithFallback();
+}
+
+const HeapVector<Member<Node>>
+HTMLSlotElement::GetDistributedNodesWithFallback() const {

[hayato, 2017/05/16 07:50:07]

The concept of DistributedNodes includes Fallback elements. So this name would
be confusing.

I rather name this just 'GetDistributedNodes'.

Couldn't we unify this with GetDistributedNodesForBinding?
Something is wrong if the only difference between them is DCHECK().
That implies that we should use DCHECK() for both cases.

Could you pursue to unify them?

   if (SupportsDistribution())
     return distributed_nodes_;
-
-  // If a slot does not support distribution, its m_distributedNodes should not
+  // If a slot does not support distribution, its distributed_nodes_ should not
   // be used.  Instead, calculate distribution manually here. This happens only
   // in a slot in non-shadow trees, so its assigned nodes are always empty.
   HeapVector<Member<Node>> distributed_nodes;
@@ -132,8 +136,12 @@ void HTMLSlotElement::AppendDistributedNode(Node& node) {
 
 void HTMLSlotElement::AppendDistributedNodesFrom(const HTMLSlotElement& other) {
   size_t index = distributed_nodes_.size();
-  distributed_nodes_.AppendVector(other.distributed_nodes_);
-  for (const auto& node : other.distributed_nodes_)
+
+  const HeapVector<Member<Node>>& other_distributed_nodes =
+      other.GetDistributedNodesWithFallback();
+  distributed_nodes_.AppendVector(other_distributed_nodes);
+
+  for (const auto& node : other_distributed_nodes)
     distributed_indices_.Set(node.Get(), index++);
 }