[mono-video, bugfix] Don't signal uv_mode in monochrome mode

BUG=aomedia:1337

Change-Id: I8ee53feb83cee8f722d76fd050a477ffe230a433

av1/decoder/decodemv.c

diff --git a/av1/decoder/decodemv.c b/av1/decoder/decodemv.c
index 543fd56..9af2aa3 100644
--- a/av1/decoder/decodemv.c
+++ b/av1/decoder/decodemv.c
@@ -1077,8 +1077,15 @@
 
   mbmi->mode = read_intra_mode(r, get_y_mode_cdf(ec_ctx, above_mi, left_mi));
 
+#if CONFIG_MONO_VIDEO
+  if (!cm->seq_params.monochrome &&
+      is_chroma_reference(mi_row, mi_col, bsize, xd->plane[1].subsampling_x,
+                          xd->plane[1].subsampling_y))
+#else
   if (is_chroma_reference(mi_row, mi_col, bsize, xd->plane[1].subsampling_x,
-                          xd->plane[1].subsampling_y)) {
+                          xd->plane[1].subsampling_y))
+#endif  // CONFIG_MONO_VIDEO
+  {
 #if !CONFIG_CFL
     mbmi->uv_mode = read_intra_mode_uv(ec_ctx, r, mbmi->mode);
 #else
@@ -1384,8 +1391,15 @@
 
   mbmi->mode = read_intra_mode(r, ec_ctx->y_mode_cdf[size_group_lookup[bsize]]);
 
+#if CONFIG_MONO_VIDEO
+  if (!cm->seq_params.monochrome &&
+      is_chroma_reference(mi_row, mi_col, bsize, xd->plane[1].subsampling_x,
+                          xd->plane[1].subsampling_y))
+#else
   if (is_chroma_reference(mi_row, mi_col, bsize, xd->plane[1].subsampling_x,
-                          xd->plane[1].subsampling_y)) {
+                          xd->plane[1].subsampling_y))
+#endif  // CONFIG_MONO_VIDEO
+  {
 #if !CONFIG_CFL
     mbmi->uv_mode = read_intra_mode_uv(ec_ctx, r, mbmi->mode);
 #else

av1/encoder/bitstream.c

diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 289bb28..e7c6200 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -1330,8 +1330,15 @@
 
   if (!is_inter) {
     write_intra_mode(ec_ctx, bsize, mode, w);
+#if CONFIG_MONO_VIDEO
+    if (!cm->seq_params.monochrome &&
+        is_chroma_reference(mi_row, mi_col, bsize, xd->plane[1].subsampling_x,
+                            xd->plane[1].subsampling_y))
+#else
     if (is_chroma_reference(mi_row, mi_col, bsize, xd->plane[1].subsampling_x,
-                            xd->plane[1].subsampling_y)) {
+                            xd->plane[1].subsampling_y))
+#endif  // CONFIG_MONO_VIDEO
+    {
 #if !CONFIG_CFL
       write_intra_uv_mode(ec_ctx, mbmi->uv_mode, mode, w);
 #else
@@ -1643,8 +1650,15 @@
 
   write_intra_mode_kf(ec_ctx, mi, above_mi, left_mi, mbmi->mode, w);
 
+#if CONFIG_MONO_VIDEO
+  if (!cm->seq_params.monochrome &&
+      is_chroma_reference(mi_row, mi_col, bsize, xd->plane[1].subsampling_x,
+                          xd->plane[1].subsampling_y))
+#else
   if (is_chroma_reference(mi_row, mi_col, bsize, xd->plane[1].subsampling_x,
-                          xd->plane[1].subsampling_y)) {
+                          xd->plane[1].subsampling_y))
+#endif  // CONFIG_MONO_VIDEO
+  {
 #if !CONFIG_CFL
     write_intra_uv_mode(ec_ctx, mbmi->uv_mode, mbmi->mode, w);
 #else