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

components/gcm_driver/common/gcm_messages.h

 // 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.
 
 #ifndef COMPONENTS_GCM_DRIVER_COMMON_GCM_MESSAGES_H_
 #define COMPONENTS_GCM_DRIVER_COMMON_GCM_MESSAGES_H_
 
 #include <map>
 #include <string>
 
 #include "components/gcm_driver/common/gcm_driver_export.h"
 
 namespace gcm {
 
 // Message data consisting of key-value pairs.
 typedef std::map<std::string, std::string> MessageData;
 
 // Message to be delivered to the other party.
 struct GCM_DRIVER_EXPORT OutgoingMessage {
   OutgoingMessage();
+  OutgoingMessage(const OutgoingMessage& other);
   ~OutgoingMessage();
 
   // Message ID.
   std::string id;
   // In seconds.
   int time_to_live;
   MessageData data;
 
   static const int kMaximumTTL;
 };
 
 // Message being received from the other party.
 struct GCM_DRIVER_EXPORT IncomingMessage {
   IncomingMessage();
+  IncomingMessage(const IncomingMessage& other);
   ~IncomingMessage();
 
   MessageData data;
   std::string collapse_key;
   std::string sender_id;
   std::string raw_data;
 
   // Whether the contents of the message have been decrypted, and are
   // available in |raw_data|.
   bool decrypted;
 };
 
 }  // namespace gcm
 
 #endif  // COMPONENTS_GCM_DRIVER_COMMON_GCM_MESSAGES_H_