Add more out of line copy ctors for complex classes.

tools/gn/bundle_file_rule.h

 // Copyright 2016 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_BUNDLE_FILE_RULE_H_
 #define TOOLS_GN_BUNDLE_FILE_RULE_H_
 
 #include <vector>
 
 #include "tools/gn/source_file.h"
 #include "tools/gn/substitution_pattern.h"
 
 class BundleData;
 class Settings;
 class SourceFile;
 class OutputFile;
 
 // BundleFileRule contains the information found in a "bundle_data" target.
 class BundleFileRule {
  public:
   BundleFileRule(const std::vector<SourceFile> sources,
                  const SubstitutionPattern& pattern);
+  BundleFileRule(const BundleFileRule& other);
   ~BundleFileRule();
 
   // Applies the substitution pattern to a source file, returning the result
   // as either a SourceFile or an OutputFile.
   SourceFile ApplyPatternToSource(const Settings* settings,
                                   const BundleData& bundle_data,
                                   const SourceFile& source_file) const;
   OutputFile ApplyPatternToSourceAsOutputFile(
       const Settings* settings,
       const BundleData& bundle_data,
       const SourceFile& source_file) const;
 
   // Returns the list of SourceFiles.
   const std::vector<SourceFile>& sources() const { return sources_; }
 
  private:
   std::vector<SourceFile> sources_;
   SubstitutionPattern pattern_;
 };
 
 #endif  // TOOLS_GN_BUNDLE_FILE_RULE_H_