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

tools/gn/substitution_list.h

 // 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.
 
 #ifndef TOOLS_GN_SUBSTITUTION_LIST_H_
 #define TOOLS_GN_SUBSTITUTION_LIST_H_
 
 #include <string>
 #include <vector>
 
 #include "tools/gn/substitution_pattern.h"
 
 // Represents a list of strings with {{substitution_patterns}} in them.
 class SubstitutionList {
  public:
   SubstitutionList();
+  SubstitutionList(const SubstitutionList& other);
   ~SubstitutionList();
 
   bool Parse(const Value& value, Err* err);
   bool Parse(const std::vector<std::string>& values,
              const ParseNode* origin,
              Err* err);
 
   // Makes a SubstitutionList from the given hardcoded patterns.
   static SubstitutionList MakeForTest(
       const char* a,
@@ skipping 10 matching lines @@
 
   void FillRequiredTypes(SubstitutionBits* bits) const;
 
  private:
   std::vector<SubstitutionPattern> list_;
 
   std::vector<SubstitutionType> required_types_;
 };
 
 #endif  // TOOLS_GN_SUBSTITUTION_LIST_H_