libvpx: Pull from upstream

source/libvpx/vp9/encoder/vp9_svc_layercontext.c

 /*
  *  Copyright (c) 2014 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 205 matching lines @@
   ++lc->current_video_frame_in_layer;
 }
 
 int vp9_is_upper_layer_key_frame(const VP9_COMP *const cpi) {
   return cpi->use_svc &&
          cpi->svc.number_temporal_layers == 1 &&
          cpi->svc.spatial_layer_id > 0 &&
          cpi->svc.layer_context[cpi->svc.spatial_layer_id].is_key_frame;
 }
 
+#if CONFIG_SPATIAL_SVC
 int vp9_svc_lookahead_push(const VP9_COMP *const cpi, struct lookahead_ctx *ctx,
                            YV12_BUFFER_CONFIG *src, int64_t ts_start,
                            int64_t ts_end, unsigned int flags) {
   struct lookahead_entry *buf;
   int i, index;
 
   if (vp9_lookahead_push(ctx, src, ts_start, ts_end, flags))
     return 1;
 
   index = ctx->write_idx - 1;
@@ skipping 109 matching lines @@
       // spatial_layer to -1 for lower layers.
       buf->svc_params[cpi->svc.spatial_layer_id].spatial_layer = -1;
       if (cpi->svc.spatial_layer_id == cpi->svc.number_spatial_layers - 1) {
         vp9_lookahead_pop(ctx, drain);
       }
     }
   }
 
   return buf;
 }
+#endif