Extend IntraBC to 4x4

Change-Id: I3f30c35bcd1bc623ad0c34c4b954ff71b2fcfd00
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index dd0e43b..799ee81 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -2169,7 +2169,7 @@
                        !xd->lossless[mbmi->segment_id];
 
 #if CONFIG_INTRABC
-  if (bsize >= BLOCK_8X8 && cm->allow_screen_content_tools) {
+  if (av1_allow_intrabc(bsize, cm)) {
     int use_intrabc = is_intrabc_block(mbmi);
     aom_write_symbol(w, use_intrabc, ec_ctx->intrabc_cdf, 2);
     if (use_intrabc) {