Cherry-pick potential divide-by-zero fix

source/libvpx/vp9/common/vp9_prob.c

Index: source/libvpx/vp9/common/vp9_prob.c
diff --git a/source/libvpx/vp9/common/vp9_prob.c b/source/libvpx/vp9/common/vp9_prob.c
index a1befc63e88dbe612e70887a47fb5b565c7c69f1..3b7b9bf3b39df07a905c01ee882b659c719cdbbe 100644
--- a/source/libvpx/vp9/common/vp9_prob.c
+++ b/source/libvpx/vp9/common/vp9_prob.c
@@ -29,33 +29,25 @@ const uint8_t vp9_norm[256] = {
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
 };
 
-
 static unsigned int tree_merge_probs_impl(unsigned int i,
                                           const vp9_tree_index *tree,
                                           const vp9_prob *pre_probs,
                                           const unsigned int *counts,
-                                          unsigned int count_sat,
-                                          unsigned int max_update,
                                           vp9_prob *probs) {
   const int l = tree[i];
   const unsigned int left_count = (l <= 0)
                  ? counts[-l]
-                 : tree_merge_probs_impl(l, tree, pre_probs, counts,
-                                         count_sat, max_update, probs);
+                 : tree_merge_probs_impl(l, tree, pre_probs, counts, probs);
   const int r = tree[i + 1];
   const unsigned int right_count = (r <= 0)
                  ? counts[-r]
-                 : tree_merge_probs_impl(r, tree, pre_probs, counts,
-                                         count_sat, max_update, probs);
+                 : tree_merge_probs_impl(r, tree, pre_probs, counts, probs);
   const unsigned int ct[2] = { left_count, right_count };
-  probs[i >> 1] = merge_probs(pre_probs[i >> 1], ct,
-                              count_sat, max_update);
+  probs[i >> 1] = mode_mv_merge_probs(pre_probs[i >> 1], ct);
   return left_count + right_count;
 }
 
 void vp9_tree_merge_probs(const vp9_tree_index *tree, const vp9_prob *pre_probs,
-                          const unsigned int *counts, unsigned int count_sat,
-                          unsigned int max_update_factor, vp9_prob *probs) {
-  tree_merge_probs_impl(0, tree, pre_probs, counts, count_sat,
-                        max_update_factor, probs);
+                          const unsigned int *counts, vp9_prob *probs) {
+  tree_merge_probs_impl(0, tree, pre_probs, counts, probs);
 }