Use std::deque for storing edges and children in heap snapshot.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index 1dad8c5d12f34c46b3abc89e7ba6ad0f92d29e42..f10ef6243da61135743fc2effaa6e787df4d0d99 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -9513,13 +9513,12 @@ size_t HeapGraphNode::GetShallowSize() const {
 
 
 int HeapGraphNode::GetChildrenCount() const {
-  return ToInternal(this)->children().length();
+  return ToInternal(this)->children_count();
 }
 
 
 const HeapGraphEdge* HeapGraphNode::GetChild(int index) const {
-  return reinterpret_cast<const HeapGraphEdge*>(
-      ToInternal(this)->children()[index]);
+  return reinterpret_cast<const HeapGraphEdge*>(ToInternal(this)->child(index));
 }