Cherry pick buffer re-allocation fix

source/libvpx/vp9/decoder/vp9_decoder.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 32 matching lines @@
     vp9_rtcd();
     vpx_dsp_rtcd();
     vpx_scale_rtcd();
     vp9_init_intra_predictors();
     init_done = 1;
   }
 }
 
 static void vp9_dec_setup_mi(VP9_COMMON *cm) {
   cm->mi = cm->mip + cm->mi_stride + 1;
-  memset(cm->mip, 0, cm->mi_stride * (cm->mi_rows + 1) * sizeof(*cm->mip));
   cm->mi_grid_visible = cm->mi_grid_base + cm->mi_stride + 1;
   memset(cm->mi_grid_base, 0,
          cm->mi_stride * (cm->mi_rows + 1) * sizeof(*cm->mi_grid_base));
 }
 
 static int vp9_dec_alloc_mi(VP9_COMMON *cm, int mi_size) {
   cm->mip = vpx_calloc(mi_size, sizeof(*cm->mip));
   if (!cm->mip)
     return 1;
   cm->mi_alloc_size = mi_size;
@@ skipping 431 matching lines @@
 
         for (j = 0; j < mag; ++j)
           this_sz |= (*x++) << (j * 8);
         sizes[i] = this_sz;
       }
       *count = frames;
     }
   }
   return VPX_CODEC_OK;
 }