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

tools/gn/substitution_pattern.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_pattern.h"
 
 #include <stddef.h>
 
 #include "base/strings/string_number_conversions.h"
 #include "tools/gn/build_settings.h"
@@ skipping 10 matching lines @@
     : type(t),
       literal(l) {
 }
 
 SubstitutionPattern::Subrange::~Subrange() {
 }
 
 SubstitutionPattern::SubstitutionPattern() : origin_(nullptr) {
 }
 
+SubstitutionPattern::SubstitutionPattern(const SubstitutionPattern& other) =
+    default;
+
 SubstitutionPattern::~SubstitutionPattern() {
 }
 
 bool SubstitutionPattern::Parse(const Value& value, Err* err) {
   if (!value.VerifyTypeIs(Value::STRING, err))
     return false;
   return Parse(value.string_value(), value.origin(), err);
 }
 
 bool SubstitutionPattern::Parse(const std::string& str,
@@ skipping 99 matching lines @@
           "File is not inside output directory.",
           "The given file should be in the output directory. Normally you\n"
           "would specify\n\"$target_out_dir/foo\" or "
           "\"{{source_gen_dir}}/foo\".");
       return false;
     }
   }
 
   return true;
 }