Turn on pruning obmc feature at speed 2

Turned on pruning obmc feature at speed 2 for encoder
speedups.

Borg test and speedup results at speed 2:
      avg_psnr: ovr_psnr: ssim:   avg_speedup(whole set)
hdres:  0.050    0.052   0.051      2.0%
midres: 0.037    0.034   0.022      1.8%

STATS_CHANGED

Change-Id: Ib4f8a1474349532c6cdb92da98bdf04eeed0732d
diff --git a/av1/encoder/encoder.c b/av1/encoder/encoder.c
index a94467d..a4018f1 100644
--- a/av1/encoder/encoder.c
+++ b/av1/encoder/encoder.c
@@ -5049,7 +5049,10 @@
   if (cpi->sf.prune_obmc_using_stats &&
       cm->current_frame.frame_type == KEY_FRAME) {
     av1_copy(cpi->obmc_probs, default_obmc_probs);
-    cpi->obmc_probs_thresh = 16;
+    if (cpi->sf.prune_obmc_using_stats == 1)
+      cpi->obmc_probs_thresh = 8;
+    else
+      cpi->obmc_probs_thresh = 16;
   }
 
   // Loop variables
diff --git a/av1/encoder/speed_features.c b/av1/encoder/speed_features.c
index 22f355f..4ed735f 100644
--- a/av1/encoder/speed_features.c
+++ b/av1/encoder/speed_features.c
@@ -186,6 +186,11 @@
     }
 
     if (is_480p_or_larger) sf->tx_type_search.prune_tx_type_using_stats = 1;
+
+    if (is_720p_or_larger)
+      sf->prune_obmc_using_stats = 2;
+    else
+      sf->prune_obmc_using_stats = 1;
   }
 
   if (speed >= 3) {
@@ -208,6 +213,8 @@
     }
 
     if (is_480p_or_larger) sf->tx_type_search.prune_tx_type_using_stats = 2;
+
+    sf->prune_obmc_using_stats = 2;
   }
 }
 
@@ -443,7 +450,6 @@
     // sf->tx_domain_dist_level = 2;
     sf->tx_domain_dist_thres_level = 2;
     sf->simple_motion_search_prune_agg = 2;
-    sf->prune_obmc_using_stats = 1;
   }
 }