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

media/base/text_track_config.cc

 // 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.
 
 #include "media/base/text_track_config.h"
 
 namespace media {
 
 TextTrackConfig::TextTrackConfig()
     : kind_(kTextNone) {
 }
 
 TextTrackConfig::TextTrackConfig(TextKind kind,
                                  const std::string& label,
                                  const std::string& language,
                                  const std::string& id)
     : kind_(kind),
       label_(label),
       language_(language),
       id_(id) {
 }
 
+TextTrackConfig::TextTrackConfig(const TextTrackConfig& other) = default;
+
 bool TextTrackConfig::Matches(const TextTrackConfig& config) const {
   return config.kind() == kind_ &&
          config.label() == label_ &&
          config.language() == language_ &&
          config.id() == id_;
 }
 
 }  // namespace media