The WebVTT parsing algorithm allows empty cue text

Source/core/html/track/WebVTTParser.cpp

 /*
  * Copyright (C) 2011 Google Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 354 matching lines @@
 }
 
 PassRefPtr<DocumentFragment> WebVTTParser::createDocumentFragmentFromCueText(Document& document, const String& cueText)
 {
     WebVTTTreeBuilder treeBuilder(document);
     return treeBuilder.buildFromString(cueText);
 }
 
 void WebVTTParser::createNewCue()
 {
-    if (!m_currentContent.length())
-        return;
-
     RefPtr<TextTrackCue> cue = TextTrackCue::create(*m_document, m_currentStartTime, m_currentEndTime, m_currentContent.toString());
     cue->setId(m_currentId);
     cue->setCueSettings(m_currentSettings);
 
     m_cuelist.append(cue);
     if (m_client)
         m_client->newCuesParsed();
 }
 
 void WebVTTParser::resetCueValues()
@@ skipping 173 matching lines @@
 }
 
 void WebVTTParser::skipWhiteSpace(const String& line, unsigned* position)
 {
     while (*position < line.length() && isASpace(line[*position]))
         (*position)++;
 }
 
 }