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

chrome/browser/media/router/media_sink.cc

 // Copyright 2015 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 "chrome/browser/media/router/media_sink.h"
 
 namespace media_router {
 
 MediaSink::MediaSink(const MediaSink::Id& sink_id,
                      const std::string& name,
                      const MediaSink::IconType icon_type)
     : sink_id_(sink_id), name_(name), icon_type_(icon_type) {}
 
+MediaSink::MediaSink(const MediaSink& other) = default;
+
 MediaSink::~MediaSink() {
 }
 
 bool MediaSink::Equals(const MediaSink& other) const {
   return sink_id_ == other.sink_id_;
 }
 
 }  // namespace media_router