Ignore aud and sei NALus when parsing bitstream.

We currently don't know how to parse these NALus and we don't need
any information from them anyway so we might as well skip parsing them
and not break.

BUG=chromium:697795

Review-Url: https://codereview.webrtc.org/2732623002
Cr-Commit-Position: refs/heads/master@{#17057}

webrtc/common_video/h264/h264_bitstream_parser.cc

@@ -283,6 +283,9 @@ void H264BitstreamParser::ParseSlice(const uint8_t* slice, size_t length) {
         LOG(LS_WARNING) << "Unable to parse PPS from H264 bitstream.";
       break;
     }
+    case H264::NaluType::kAud:
+    case H264::NaluType::kSei:
+      break;  // Ignore these nalus, as we don't care about their contents.
     default:
       Result res = ParseNonParameterSetNalu(slice, length, nalu_type);
       if (res != kOk)