libvpx: Pull from upstream

source/libvpx/vp9/decoder/vp9_decoder.c

Index: source/libvpx/vp9/decoder/vp9_decoder.c
===================================================================
--- source/libvpx/vp9/decoder/vp9_decoder.c	(revision 290053)
+++ source/libvpx/vp9/decoder/vp9_decoder.c	(working copy)
@@ -123,8 +123,12 @@
    * later commit that adds VP9-specific controls for this functionality.
    */
   if (ref_frame_flag == VP9_LAST_FLAG) {
-    const YV12_BUFFER_CONFIG *const cfg =
-        &cm->frame_bufs[cm->ref_frame_map[0]].buf;
+    const YV12_BUFFER_CONFIG *const cfg = get_ref_frame(cm, 0);
+    if (cfg == NULL) {
+      vpx_internal_error(&cm->error, VPX_CODEC_ERROR,
+                         "No 'last' reference frame");
+      return VPX_CODEC_ERROR;
+    }
     if (!equal_dimensions(cfg, sd))
       vpx_internal_error(&cm->error, VPX_CODEC_ERROR,
                          "Incorrect buffer dimensions");
@@ -181,17 +185,6 @@
   return cm->error.error_code;
 }
 
-
-int vp9_get_reference_dec(VP9Decoder *pbi, int index, YV12_BUFFER_CONFIG **fb) {
-  VP9_COMMON *cm = &pbi->common;
-
-  if (index < 0 || index >= REF_FRAMES)
-    return -1;
-
-  *fb = &cm->frame_bufs[cm->ref_frame_map[index]].buf;
-  return 0;
-}
-
 /* If any buffer updating is signaled it should be done here. */
 static void swap_frame_buffers(VP9Decoder *pbi) {
   int ref_index = 0, mask;