[NORMATIVE] Move frame_offset setup upwards

This CL is to set up the frame_offset (which is OrderHint in the spec)
earlier, inside the read_uncompressed_header(), as is needed by the
later handling of frame_refs_short_signaling.

BUG=aomedia:1484

Change-Id: Ie5d85c1caa36354ec3f98129eb247eb700389081
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 11512a4..0f4334a 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -3083,6 +3083,17 @@
   cm->frame_refs_short_signaling = 0;
 #endif  // CONFIG_FRAME_REFS_SIGNALING
 
+  if (cm->show_frame == 0) {
+    int arf_offset = AOMMIN(
+        (MAX_GF_INTERVAL - 1),
+        cpi->twopass.gf_group.arf_src_offset[cpi->twopass.gf_group.index]);
+    int brf_offset =
+        cpi->twopass.gf_group.brf_src_offset[cpi->twopass.gf_group.index];
+
+    arf_offset = AOMMIN((MAX_GF_INTERVAL - 1), arf_offset + brf_offset);
+    aom_wb_write_literal(wb, arf_offset, FRAME_OFFSET_BITS);
+  }
+
   if (cm->frame_type == KEY_FRAME) {
     write_frame_size(cm, frame_size_override_flag, wb);
     assert(av1_superres_unscaled(cm) ||
@@ -3234,17 +3245,6 @@
     }
   }
 
-  if (cm->show_frame == 0) {
-    int arf_offset = AOMMIN(
-        (MAX_GF_INTERVAL - 1),
-        cpi->twopass.gf_group.arf_src_offset[cpi->twopass.gf_group.index]);
-    int brf_offset =
-        cpi->twopass.gf_group.brf_src_offset[cpi->twopass.gf_group.index];
-
-    arf_offset = AOMMIN((MAX_GF_INTERVAL - 1), arf_offset + brf_offset);
-    aom_wb_write_literal(wb, arf_offset, FRAME_OFFSET_BITS);
-  }
-
   if (cm->seq_params.frame_id_numbers_present_flag) {
     cm->refresh_mask =
         cm->frame_type == KEY_FRAME ? 0xFF : get_refresh_mask(cpi);