[NORMATIVE] Renable frame refs signaling for ER.

Now that OrderHints are explicitly signaled, there is
no need to disable short refs signaling.

Change-Id: Id9547d0eaf29b2d8c742b108011357dbd07d7204
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index bb316f2..bfc6734 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -3178,12 +3178,10 @@
       }
 
 #if CONFIG_FRAME_REFS_SIGNALING
-      // TODO(zoeliu@google.com): To complete the encoder-side implementation
-      // for the scenario cm->frame_refs_short_signaling == 1.
       assert(cm->frame_refs_short_signaling == 0);
       // NOTE: Error resilient mode turns off frame_refs_short_signaling
       //       automatically.
-      if (!cm->error_resilient_mode && cm->seq_params.enable_order_hint)
+      if (cm->seq_params.enable_order_hint)
         aom_wb_write_bit(wb, cm->frame_refs_short_signaling);
       else
         assert(cm->frame_refs_short_signaling == 0);