libvpx: Pull from upstream

source/libvpx/vp8/decoder/threading.c

 /*
  *  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 78 matching lines @@
         pbi->mt_current_mb_col[i] = -1;
 }
 
 static void mt_decode_macroblock(VP8D_COMP *pbi, MACROBLOCKD *xd,
                                  unsigned int mb_idx)
 {
     MB_PREDICTION_MODE mode;
     int i;
 #if CONFIG_ERROR_CONCEALMENT
     int corruption_detected = 0;
+#else
+    (void)mb_idx;
 #endif
 
     if (xd->mode_info_context->mbmi.mb_skip_coeff)
     {
         vp8_reset_mb_tokens_context(xd);
     }
     else if (!vp8dx_bool_error(xd->current_bc))
     {
         int eobtotal;
         eobtotal = vp8_decode_mb_tokens(pbi, xd);
@@ skipping 792 matching lines @@
 
     setup_decoding_thread_data(pbi, xd, pbi->mb_row_di, pbi->decoding_thread_count);
 
     for (i = 0; i < pbi->decoding_thread_count; i++)
         sem_post(&pbi->h_event_start_decoding[i]);
 
     mt_decode_mb_rows(pbi, xd, 0);
 
     sem_wait(&pbi->h_event_end_decoding);   /* add back for each frame */
 }