Fixup h264stream test.

This should be updated with stubbed methods when it gets re-written so
that we can actually stub methods.

@@ -70,6 +70,9 @@ test('starting PTS values can be negative', function() {
       nalUnitTypes.access_unit_delimiter_rbsp
     ]);
 
+  // add a "tag" to the stream so that it doesn't try and parse metadata
+  h264Stream.tags.push('spacer tag');
+
   h264Stream.setTimeStampOffset(-100);
   h264Stream.setNextTimeStamp(-100, -100, true);
   h264Stream.writeBytes(accessUnitDelimiter, 0, accessUnitDelimiter.byteLength);
@@ -80,6 +83,8 @@ test('starting PTS values can be negative', function() {
   // flush out the last tag
   h264Stream.writeBytes(accessUnitDelimiter, 0, accessUnitDelimiter.byteLength);
 
+  h264Stream.tags.shift();
+
   strictEqual(h264Stream.tags.length, 3, 'three tags are ready');
   strictEqual(h264Stream.tags[0].pts, 0, 'the first PTS is zero');
   strictEqual(h264Stream.tags[0].dts, 0, 'the first DTS is zero');