Introduce the plumbing necessary to report Unrecoverable error from model safe workers.

chrome/browser/sync/internal_api/sync_manager.cc

Index: chrome/browser/sync/internal_api/sync_manager.cc
diff --git a/chrome/browser/sync/internal_api/sync_manager.cc b/chrome/browser/sync/internal_api/sync_manager.cc
index c8435b65b996a08fe7dab7efb01fca927e24a726..b4fccb3edb970bc61cafb6f2461255c9a74f9038 100644
--- a/chrome/browser/sync/internal_api/sync_manager.cc
+++ b/chrome/browser/sync/internal_api/sync_manager.cc
@@ -1690,6 +1690,14 @@ void SyncManager::SyncInternal::OnSyncEngineEvent(
     return;
   }
 
+  if (event.what_happened == SyncEngineEvent::UNRECOVERABLE_ERROR) {
+    FOR_EACH_OBSERVER(SyncManager::Observer, observers_,
+                      OnUnrecoverableError(
+                          event.unrecoverable_error_info.location,
+                          event.unrecoverable_error_info.message));
+    return;
+  }
+
 }
 
 void SyncManager::SyncInternal::SetJsEventHandler(