[layoutng] fix incorrect vector sizing

third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc

Index: third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
index 7c8e546d99ba3e7126ce8b7dc1ee5248cdbe4cf1..c329866ab446aac1f0d6a3528895a25a294147bb 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
+++ b/third_party/WebKit/Source/core/layout/ng/ng_fragment_builder.cc
@@ -58,7 +58,8 @@ NGPhysicalFragment* NGFragmentBuilder::ToFragment() {
   DCHECK_EQ(offsets_.size(), children_.size());
 
   NGPhysicalSize physical_size = size_.ConvertToPhysical(writing_mode_);
-  HeapVector<Member<const NGPhysicalFragmentBase>> children(children_.size());
+  HeapVector<Member<const NGPhysicalFragmentBase>> children;
+  children.reserveCapacity(children_.size());
 
   for (size_t i = 0; i < children_.size(); ++i) {
     NGPhysicalFragmentBase* child = children_[i].get();