libvpx: Pull from upstream

source/libvpx/vp9/encoder/vp9_treewriter.c

Index: source/libvpx/vp9/encoder/vp9_treewriter.c
===================================================================
--- source/libvpx/vp9/encoder/vp9_treewriter.c	(revision 240950)
+++ source/libvpx/vp9/encoder/vp9_treewriter.c	(working copy)
@@ -36,3 +36,50 @@
   costs[-tree[0]] = vp9_cost_bit(probs[0], 0);
   cost(costs, tree, probs, 2, 0);
 }
+
+static void tree2tok(struct vp9_token *tokens, const vp9_tree_index *tree,
+                     int i, int v, int l) {
+  v += v;
+  ++l;
+
+  do {
+    const vp9_tree_index j = tree[i++];
+    if (j <= 0) {
+      tokens[-j].value = v;
+      tokens[-j].len = l;
+    } else {
+      tree2tok(tokens, tree, j, v, l);
+    }
+  } while (++v & 1);
+}
+
+void vp9_tokens_from_tree(struct vp9_token *tokens,
+                          const vp9_tree_index *tree) {
+  tree2tok(tokens, tree, 0, 0, 0);
+}
+
+static unsigned int convert_distribution(unsigned int i, vp9_tree tree,
+                                         unsigned int branch_ct[][2],
+                                         const unsigned int num_events[]) {
+  unsigned int left, right;
+
+  if (tree[i] <= 0)
+    left = num_events[-tree[i]];
+  else
+    left = convert_distribution(tree[i], tree, branch_ct, num_events);
+
+  if (tree[i + 1] <= 0)
+    right = num_events[-tree[i + 1]];
+  else
+    right = convert_distribution(tree[i + 1], tree, branch_ct, num_events);
+
+  branch_ct[i >> 1][0] = left;
+  branch_ct[i >> 1][1] = right;
+  return left + right;
+}
+
+void vp9_tree_probs_from_distribution(vp9_tree tree,
+                                      unsigned int branch_ct[/* n-1 */][2],
+                                      const unsigned int num_events[/* n */]) {
+  convert_distribution(0, tree, branch_ct, num_events);
+}