tools/gn: Add out-of-line copy ctors for complex classes.

tools/gn/substitution_list.cc

 // Copyright 2014 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 "tools/gn/substitution_list.h"
 
 #include <stddef.h>
 #include <string.h>
 
 #include "tools/gn/value.h"
 
 SubstitutionList::SubstitutionList() {
 }
 
+SubstitutionList::SubstitutionList(const SubstitutionList& other) = default;
+
 SubstitutionList::~SubstitutionList() {
 }
 
 bool SubstitutionList::Parse(const Value& value, Err* err) {
   if (!value.VerifyTypeIs(Value::LIST, err))
     return false;
 
   const std::vector<Value>& input_list = value.list_value();
   list_.resize(input_list.size());
   for (size_t i = 0; i < input_list.size(); i++) {
@@ skipping 36 matching lines @@
   Err err;
   SubstitutionList result;
   result.Parse(input_strings, nullptr, &err);
   return result;
 }
 
 void SubstitutionList::FillRequiredTypes(SubstitutionBits* bits) const {
   for (const auto& item : list_)
     item.FillRequiredTypes(bits);
 }