[Sync] Make SMTP always have the dump stack function.

components/sync/driver/directory_data_type_controller.h

Index: components/sync/driver/directory_data_type_controller.h
diff --git a/components/sync/driver/directory_data_type_controller.h b/components/sync/driver/directory_data_type_controller.h
index b4b2777894bfe0a1917aba93752286f1a84be48e..857055c062f83e32f85dfc08ffe28cedab239c36 100644
--- a/components/sync/driver/directory_data_type_controller.h
+++ b/components/sync/driver/directory_data_type_controller.h
@@ -66,6 +66,9 @@ class DirectoryDataTypeController : public DataTypeController {
   // Returns null if the ChangeProcessor isn't created or connected.
   virtual ChangeProcessor* GetChangeProcessor() const = 0;
 
+  // Function to capture and upload a stack trace when an error occurs.
+  base::Closure dump_stack_;
+
   SyncClient* const sync_client_;
 
  private: