Abort sync cycles when download step fails

sync/test/engine/mock_connection_manager.cc

Index: sync/test/engine/mock_connection_manager.cc
diff --git a/sync/test/engine/mock_connection_manager.cc b/sync/test/engine/mock_connection_manager.cc
index ab95bce6f2afe92e3fb39c5b03603b7034417f68..127e85887a1c4b29ed1c14a3f38054b72e3859af 100644
--- a/sync/test/engine/mock_connection_manager.cc
+++ b/sync/test/engine/mock_connection_manager.cc
@@ -48,7 +48,7 @@ MockConnectionManager::MockConnectionManager(syncable::Directory* directory)
       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),
@@ -111,8 +111,9 @@ bool MockConnectionManager::PostBufferToPath(PostBufferParams* params,
     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;
   }