Add dependent_horztilegroups experiment

This adds part of the proposal in "AV1 Tile Overview v1_1".
A new dependent_horztilegroups configure option is added
(disabled by default).

The experiment adds syntax dependencies between tile groups.

Change-Id: I6721875d622807f92f578ab1d2a5d32bff6f472f

av1/common/tile_common.c

diff --git a/av1/common/tile_common.c b/av1/common/tile_common.c
index 3ddcc86..de97ccf 100644
--- a/av1/common/tile_common.c
+++ b/av1/common/tile_common.c
@@ -19,10 +19,19 @@
 #if CONFIG_DEPENDENT_HORZTILES
 void av1_tile_set_tg_boundary(TileInfo *tile, const AV1_COMMON *const cm,
                               int row, int col) {
+#if CONFIG_DEPENDENT_HORZTILEGROUPS
+  (void)cm;
+  (void)col;
+#if !CONFIG_MAX_TILE
+  (void)row;
+#endif
+  tile->tg_horz_boundary = 0;
+#else
   const int tg_start_row = cm->tile_group_start_row[row][col];
   const int tg_start_col = cm->tile_group_start_col[row][col];
   tile->tg_horz_boundary = ((row == tg_start_row && col >= tg_start_col) ||
                             (row == tg_start_row + 1 && col < tg_start_col));
+#endif
 #if CONFIG_MAX_TILE
   if (cm->tile_row_independent[row]) {
     tile->tg_horz_boundary = 1;  // this tile row is independent

build/cmake/aom_config_defaults.cmake

diff --git a/build/cmake/aom_config_defaults.cmake b/build/cmake/aom_config_defaults.cmake
index 11225c6..eeaa7f1 100644
--- a/build/cmake/aom_config_defaults.cmake
+++ b/build/cmake/aom_config_defaults.cmake
@@ -123,6 +123,7 @@
 set(CONFIG_DAALA_TX_DST8 0 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_DCT_ONLY 0 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_DEBLOCK_13TAP 1 CACHE NUMBER "AV1 experiment flag.")
+set(CONFIG_DEPENDENT_HORZTILEGROUPS 0 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_DEPENDENT_HORZTILES 0 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_DIST_8X8 1 CACHE NUMBER "AV1 experiment flag.")
 set(CONFIG_DUAL_FILTER 1 CACHE NUMBER "AV1 experiment flag.")

configure

diff --git a/configure b/configure
index fce85d1..2411eeb 100755
--- a/configure
+++ b/configure
@@ -290,6 +290,7 @@
     reference_buffer
     entropy_stats
     dependent_horztiles
+    dependent_horztilegroups
     dist_8x8
     palette_throughput
     ref_adapt