[Sync] Sync client should to exponential backoff when receive partial failure

components/sync/engine_impl/cycle/test_util.cc

Index: components/sync/engine_impl/cycle/test_util.cc
diff --git a/components/sync/engine_impl/cycle/test_util.cc b/components/sync/engine_impl/cycle/test_util.cc
index 347c994918655e586c1234cd583059f2c67337f4..70c94d4e3c1fd45097515c7a707267d828a577a1 100644
--- a/components/sync/engine_impl/cycle/test_util.cc
+++ b/components/sync/engine_impl/cycle/test_util.cc
@@ -97,11 +97,17 @@ void SimulateThrottledImpl(SyncCycle* cycle, const base::TimeDelta& delta) {
 void SimulateTypesThrottledImpl(SyncCycle* cycle,
                                 ModelTypeSet types,
                                 const base::TimeDelta& delta) {
-  cycle->mutable_status_controller()->set_last_download_updates_result(
-      SERVER_RETURN_THROTTLED);
+  cycle->mutable_status_controller()->set_commit_result(
+      SERVER_RETURN_PARTIAL_FAILURE);
   cycle->delegate()->OnTypesThrottled(types, delta);
 }
 
+void SimulatePartialFailureImpl(SyncCycle* cycle, ModelTypeSet types) {
+  cycle->mutable_status_controller()->set_commit_result(
+      SERVER_RETURN_PARTIAL_FAILURE);
+  cycle->delegate()->OnTypesBackedOff(types);
+}
+
 void SimulatePollIntervalUpdateImpl(ModelTypeSet requested_types,
                                     SyncCycle* cycle,
                                     const base::TimeDelta& new_poll) {