Abort sync cycles when download step fails

sync/test/engine/mock_connection_manager.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.
 //
 // Mock ServerConnectionManager class for use in client regression tests.
 
 #include "sync/test/engine/mock_connection_manager.h"
 
 #include <map>
 
@@ skipping 30 matching lines @@
 MockConnectionManager::MockConnectionManager(syncable::Directory* directory)
     : ServerConnectionManager("unused", 0, false, "version"),
       server_reachable_(true),
       conflict_all_commits_(false),
       conflict_n_commits_(0),
       next_new_id_(10000),
       store_birthday_("Store BDay!"),
       store_birthday_sent_(false),
       client_stuck_(false),
       commit_time_rename_prepended_string_(""),
-      fail_next_postbuffer_(false),
+      countdown_to_postbuffer_fail_(0),
       directory_(directory),
       mid_commit_observer_(NULL),
       throttling_(false),
       fail_with_auth_invalid_(false),
       fail_non_periodic_get_updates_(false),
       client_command_(NULL),
       next_position_in_parent_(2),
       use_legacy_bookmarks_protocol_(false),
       num_get_updates_requests_(0) {
   SetNewTimestamp(0);
@@ skipping 42 matching lines @@
     params->response.server_status = HttpResponse::SYNC_AUTH_ERROR;
     return false;
   }
 
   if (auth_token != kValidAuthToken) {
     // Simulate server-side auth failure.
     params->response.server_status = HttpResponse::SYNC_AUTH_ERROR;
     InvalidateAndClearAuthToken();
   }
 
-  if (fail_next_postbuffer_) {
-    fail_next_postbuffer_ = false;
+  if (--countdown_to_postbuffer_fail_ == 0) {
+    // Fail as countdown hits zero.
+    params->response.server_status = HttpResponse::SYNC_SERVER_ERROR;
     return false;
   }
 
   if (!server_reachable_) {
     params->response.server_status = HttpResponse::CONNECTION_UNAVAILABLE;
     return false;
   }
 
   // Default to an ok connection.
   params->response.server_status = HttpResponse::SERVER_CONNECTION_OK;
@@ skipping 497 matching lines @@
   server_reachable_ = false;
 }
 
 void MockConnectionManager::UpdateConnectionStatus() {
   if (!server_reachable_) {
     server_status_ = HttpResponse::CONNECTION_UNAVAILABLE;
   } else {
     server_status_ = HttpResponse::SERVER_CONNECTION_OK;
   }
 }