libvpx: Pull from upstream

source/libvpx/vp8/encoder/encodeframe.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 504 matching lines @@
             {
                 int b;
 
                 for (b = 0; b < xd->mbmi.partition_count; b++)
                 {
                     inter_b_modes[x->partition->bmi[b].mode] ++;
                 }
             }
 
 #endif
+            // Keep track of how many (consecutive) times a block is coded
+            // as ZEROMV_LASTREF, for base layer frames.
+            // Reset to 0 if its coded as anything else.
+            if (cpi->current_layer == 0) {
+              if (xd->mode_info_context->mbmi.mode == ZEROMV &&
+                  xd->mode_info_context->mbmi.ref_frame == LAST_FRAME) {
+                // Increment, check for wrap-around.
+                if (cpi->consec_zero_last[map_index+mb_col] < 255)
+                  cpi->consec_zero_last[map_index+mb_col] += 1;
+              } else {
+                cpi->consec_zero_last[map_index+mb_col] = 0;
+              }
+            }
 
             /* Special case code for cyclic refresh
              * If cyclic update enabled then copy xd->mbmi.segment_id; (which
              * may have been updated based on mode during
              * vp8cx_encode_inter_macroblock()) back into the global
              * segmentation map
              */
             if ((cpi->current_layer == 0) &&
                 (cpi->cyclic_refresh_mode_enabled &&
                  xd->segmentation_enabled))
@@ skipping 860 matching lines @@
             vp8_fix_contexts(xd);
         }
         else
         {
             vp8_stuff_mb(cpi, x, t);
         }
     }
 
     return rate;
 }