Update segment tree_cdf per frame.

Move computing the segmentation_probs.tree_cdf table per symbol to
 computing it only when the probabilities are updated.

Change-Id: I3826418094bbaca4ded87de5ff04d4b27c85e35a

av1/decoder/decodeframe.c

@@ -3672,6 +3672,10 @@ static int read_compressed_header(AV1Decoder *pbi, const uint8_t *data,
     }
     for (k = 0; k < MAX_SEGMENTS - 1; k++)
       av1_diff_update_prob(&r, &cm->fc->seg.tree_probs[k]);
+#if CONFIG_DAALA_EC
+    av1_tree_to_cdf(av1_segment_tree, cm->fc->seg.tree_probs,
+                    cm->fc->seg.tree_cdf);
+#endif
   }
 
   for (j = 0; j < INTRA_MODES; j++)