[Sync] Add support for performing a GetKey on startup.

sync/engine/syncer_proto_util.cc

 // Copyright (c) 2012 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 "sync/engine/syncer_proto_util.h"
 
 #include "base/format_macros.h"
 #include "base/stringprintf.h"
 #include "sync/engine/net/server_connection_manager.h"
 #include "sync/engine/syncer.h"
@@ skipping 329 matching lines @@
 
 // static
 SyncerError SyncerProtoUtil::PostClientToServerMessage(
     const ClientToServerMessage& msg,
     ClientToServerResponse* response,
     SyncSession* session) {
 
   CHECK(response);
   DCHECK(!msg.get_updates().has_from_timestamp());  // Deprecated.
   DCHECK(!msg.get_updates().has_requested_types());  // Deprecated.
-  DCHECK(msg.has_store_birthday() || IsVeryFirstGetUpdates(msg))
+  DCHECK(msg.has_store_birthday() ||
+         IsVeryFirstGetUpdates(msg) ||
+         msg.has_get_encryption_key())
       << "Must call AddRequestBirthday to set birthday.";
 
   syncable::Directory* dir = session->context()->directory();
 
   LogClientToServerMessage(msg);
   session->context()->traffic_recorder()->RecordClientToServerMessage(msg);
   if (!PostAndProcessHeaders(session->context()->connection_manager(), session,
                              msg, response)) {
     // There was an error establishing communication with the server.
     // We can not proceed beyond this point.
@@ skipping 186 matching lines @@
 std::string SyncerProtoUtil::ClientToServerResponseDebugString(
     const ClientToServerResponse& response) {
   // Add more handlers as needed.
   std::string output;
   if (response.has_get_updates())
     output.append(GetUpdatesResponseString(response.get_updates()));
   return output;
 }
 
 }  // namespace syncer