Bug 1269768 - Treat multiple BlockAdditions elements in WebM as an error. r=giles

media/libnestegg/README_MOZILLA

@@ -5,4 +5,4 @@ Makefile.in build files for the Mozilla build system.
 
 The nestegg git repository is: git://github.com/kinetiknz/nestegg.git
 
-The git commit ID used was 39f7bf7ce5aaa11d4ebe2fb54e66e6f1a2ce4150.
+The git commit ID used was d493c8a7abd05c6911cd546fd6b5c82b366f5203.

media/libnestegg/src/nestegg.c

@@ -2412,6 +2412,9 @@ nestegg_read_packet(nestegg * ctx, nestegg_packet ** pkt)
           break;
         }
         case ID_BLOCK_ADDITIONS: {
+          /* There should only be one BlockAdditions; treat multiple as an error. */
+          if (block_additional)
+            return -1;
           r = ne_read_block_additions(ctx, size, &block_additional);
           if (r != 1)
             return r;