[Sync] Add two more USS integration tests.

components/sync/driver/non_blocking_data_type_controller.h

Index: components/sync/driver/non_blocking_data_type_controller.h
diff --git a/components/sync/driver/non_blocking_data_type_controller.h b/components/sync/driver/non_blocking_data_type_controller.h
index 9091cc576de0f011b1ae29732654fa123ba028f9..d81b8311f1932cb10557e8c851016e3f6f095fb2 100644
--- a/components/sync/driver/non_blocking_data_type_controller.h
+++ b/components/sync/driver/non_blocking_data_type_controller.h
@@ -97,6 +97,12 @@ class NonBlockingDataTypeController : public sync_driver::DataTypeController {
   // callback and must temporarily own it until ActivateDataType is called.
   std::unique_ptr<syncer_v2::ActivationContext> activation_context_;
 
+  // This is a hack to prevent reconfigurations from crashing, because USS
+  // activation is not idempotent. RegisterWithBackend only needs to actually do
+  // something the first time after the type is enabled.
+  // TODO(crbug.com/647505): Remove this once the DTM handles things better.
+  bool activated_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(NonBlockingDataTypeController);
 };