libvpx: Pull from upstream

source/libvpx/vp8/vp8_cx_iface.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 861 matching lines @@
     pick_quickcompress_mode(ctx, duration, deadline);
     vpx_codec_pkt_list_init(&ctx->pkt_list);
 
     // If no flags are set in the encode call, then use the frame flags as
     // defined via the control function: vp8e_set_frame_flags.
     if (!flags) {
         flags = ctx->control_frame_flags;
     }
     ctx->control_frame_flags = 0;
 
-    res = set_reference_and_update(ctx, flags);
+    if (!res)
+        res = set_reference_and_update(ctx, flags);
 
     /* Handle fixed keyframe intervals */
     if (ctx->cfg.kf_mode == VPX_KF_AUTO
         && ctx->cfg.kf_min_dist == ctx->cfg.kf_max_dist)
     {
         if (++ctx->fixed_kf_cntr > ctx->cfg.kf_min_dist)
         {
             flags |= VPX_EFLAG_FORCE_KF;
             ctx->fixed_kf_cntr = 1;
         }
@@ skipping 493 matching lines @@
         1,                  /* 1 cfg map */
         vp8e_usage_cfg_map, /* vpx_codec_enc_cfg_map_t    cfg_maps; */
         vp8e_encode,        /* vpx_codec_encode_fn_t      encode; */
         vp8e_get_cxdata,    /* vpx_codec_get_cx_data_fn_t   get_cx_data; */
         vp8e_set_config,
         NULL,
         vp8e_get_preview,
         vp8e_mr_alloc_mem,
     } /* encoder functions */
 };