libvpx: Pull from upstream

source/libvpx/vp9/common/vp9_treecoder.h

 /*
  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 61 matching lines @@
 
 static INLINE vp9_prob get_binary_prob(int n0, int n1) {
   return get_prob(n0, n0 + n1);
 }
 
 /* this function assumes prob1 and prob2 are already within [1,255] range */
 static INLINE vp9_prob weighted_prob(int prob1, int prob2, int factor) {
   return ROUND_POWER_OF_TWO(prob1 * (256 - factor) + prob2 * factor, 8);
 }
 
+static INLINE vp9_prob merge_probs(vp9_prob pre_prob, vp9_prob prob,
+                                   const unsigned int ct[2],
+                                   unsigned int count_sat,
+                                   unsigned int max_update_factor) {
+  const unsigned int count = MIN(ct[0] + ct[1], count_sat);
+  const unsigned int factor = max_update_factor * count / count_sat;
+  return weighted_prob(pre_prob, prob, factor);
+}
+
+static INLINE vp9_prob merge_probs2(vp9_prob pre_prob,
+                                   const unsigned int ct[2],
+                                   unsigned int count_sat,
+                                   unsigned int max_update_factor) {
+  return merge_probs(pre_prob, get_binary_prob(ct[0], ct[1]), ct, count_sat,
+                     max_update_factor);
+}
+
+
 #endif  // VP9_COMMON_VP9_TREECODER_H_