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

tools/gn/label_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/label_pattern.h"
 
 #include <stddef.h>
 
 #include "base/strings/string_util.h"
 #include "build/build_config.h"
@@ skipping 43 matching lines @@
 LabelPattern::LabelPattern(Type type,
                            const SourceDir& dir,
                            const base::StringPiece& name,
                            const Label& toolchain_label)
     : toolchain_(toolchain_label),
       type_(type),
       dir_(dir) {
   name.CopyToString(&name_);
 }
 
+LabelPattern::LabelPattern(const LabelPattern& other) = default;
+
 LabelPattern::~LabelPattern() {
 }
 
 // static
 LabelPattern LabelPattern::GetPattern(const SourceDir& current_dir,
                                       const Value& value,
                                       Err* err) {
   if (!value.VerifyTypeIs(Value::STRING, err))
     return LabelPattern();
 
@@ skipping 186 matching lines @@
       break;
   }
 
   if (!toolchain_.is_null()) {
     result.push_back('(');
     result.append(toolchain_.GetUserVisibleName(false));
     result.push_back(')');
   }
   return result;
 }