media: Add out-of-line copy ctors for complex classes.

media/base/text_track_config.h

 // Copyright 2013 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 MEDIA_BASE_TEXT_TRACK_CONFIG_H_
 #define MEDIA_BASE_TEXT_TRACK_CONFIG_H_
 
 #include <string>
 
 #include "media/base/media_export.h"
 
 namespace media {
 
 // Specifies the varieties of text tracks.
 enum TextKind {
   kTextSubtitles,
   kTextCaptions,
   kTextDescriptions,
   kTextMetadata,
   kTextNone
 };
 
 class MEDIA_EXPORT TextTrackConfig {
  public:
   TextTrackConfig();
+  TextTrackConfig(const TextTrackConfig& other);
   TextTrackConfig(TextKind kind,
                   const std::string& label,
                   const std::string& language,
                   const std::string& id);
 
   // Returns true if all fields in |config| match this config.
   bool Matches(const TextTrackConfig& config) const;
 
   TextKind kind() const { return kind_; }
   const std::string& label() const { return label_; }
   const std::string& language() const { return language_; }
   const std::string& id() const { return id_; }
 
  private:
   TextKind kind_;
   std::string label_;
   std::string language_;
   std::string id_;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_TEXT_TRACK_H_