[Sync::USS] Avoid behavioral changes in NigoriProce::ConnectIfReady()

This CL adjusts the error checking in
NigoriModelTypeProcessor::ConnectIfReady()
to avoid any behavioral changes after in-lining IsModelReadyOrError()

Bug: 922900
Change-Id: I5b0d1023bbf38d109e3b5394ee8a044de0add7b3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1583882
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#653998}
diff --git a/components/sync/nigori/nigori_model_type_processor.cc b/components/sync/nigori/nigori_model_type_processor.cc
index 2a99597..cc78a52 100644
--- a/components/sync/nigori/nigori_model_type_processor.cc
+++ b/components/sync/nigori/nigori_model_type_processor.cc
@@ -328,15 +328,14 @@
   if (!start_callback_) {
     return;
   }
-  if (!model_ready_to_sync_) {
-    return;
-  }
   if (model_error_) {
     activation_request_.error_handler.Run(model_error_.value());
     start_callback_.Reset();
     return;
   }
-  DCHECK(model_ready_to_sync_);
+  if (!model_ready_to_sync_) {
+    return;
+  }
 
   if (!model_type_state_.has_cache_guid()) {
     model_type_state_.set_cache_guid(activation_request_.cache_guid);