libvpx: Pull from upstream

source/libvpx/vp9/common/vp9_prob.c

Index: source/libvpx/vp9/common/vp9_prob.c
===================================================================
--- source/libvpx/vp9/common/vp9_prob.c	(revision 251189)
+++ source/libvpx/vp9/common/vp9_prob.c	(working copy)
@@ -28,3 +28,34 @@
   0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
   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);
+  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);
+  const unsigned int ct[2] = { left_count, right_count };
+  probs[i >> 1] = merge_probs(pre_probs[i >> 1], ct,
+                              count_sat, max_update);
+  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);
+}