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

components/browser_sync/profile_sync_service.cc

Index: components/browser_sync/profile_sync_service.cc
diff --git a/components/browser_sync/profile_sync_service.cc b/components/browser_sync/profile_sync_service.cc
index bf06a348d3d3ac774b08da706d4153df1d8744dc..5fff58bc7149b90e2d3b9c3d7aeb6f7820c7b7ae 100644
--- a/components/browser_sync/profile_sync_service.cc
+++ b/components/browser_sync/profile_sync_service.cc
@@ -1870,6 +1870,7 @@ base::Value* ProfileSyncService::GetTypeStatusMap() {
 
   SyncBackendHost::Status detailed_status = backend_->GetDetailedStatus();
   ModelTypeSet& throttled_types(detailed_status.throttled_types);
+  ModelTypeSet& backed_off_types(detailed_status.backed_off_types);
   ModelTypeSet registered = GetRegisteredDataTypes();
   std::unique_ptr<base::DictionaryValue> type_status_header(
       new base::DictionaryValue());
@@ -1914,12 +1915,18 @@ base::Value* ProfileSyncService::GetTypeStatusMap() {
     } else if (throttled_types.Has(type) && passive_types.Has(type)) {
       type_status->SetString("status", "warning");
       type_status->SetString("value", "Passive, Throttled");
+    } else if (backed_off_types.Has(type) && passive_types.Has(type)) {
+      type_status->SetString("status", "warning");
+      type_status->SetString("value", "Passive, Backed off");
     } else if (passive_types.Has(type)) {
       type_status->SetString("status", "warning");
       type_status->SetString("value", "Passive");
     } else if (throttled_types.Has(type)) {
       type_status->SetString("status", "warning");
       type_status->SetString("value", "Throttled");
+    } else if (backed_off_types.Has(type)) {
+      type_status->SetString("status", "warning");
+      type_status->SetString("value", "Backed off");
     } else if (active_types.Has(type)) {
       type_status->SetString("status", "ok");
       type_status->SetString(