Implement DataCue interface.

Source/core/html/track/TextTrack.cpp

 /*
  * Copyright (C) 2011 Google Inc.  All rights reserved.
  * Copyright (C) 2011, 2012, 2013 Apple 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.
@@ skipping 206 matching lines @@
     // then the activeCues attribute must return a live TextTrackCueList object ...
     // ... whose active flag was set when the script started, in text track cue
     // order. Otherwise, it must return null. When an object is returned, the
     // same object must be returned each time.
     // http://www.whatwg.org/specs/web-apps/current-work/#dom-texttrack-activecues
     if (m_cues && m_mode != disabledKeyword())
         return m_cues->activeCues();
     return 0;
 }
 
-void TextTrack::addCue(PassRefPtr<TextTrackCue> prpCue)
+void TextTrack::addCue(PassRefPtr<TextTrackCue> prpCue, ExceptionState& exceptionState)
 {
     if (!prpCue)
         return;
 
     RefPtr<TextTrackCue> cue = prpCue;
 
+    // 4.7.10.12.6 Text tracks exposing in-band metadata
+    // The UA will use DataCue to expose only text track cue objects that belong to a text track that has a text
+    // track kind of metadata.
+    // If a DataCue is added to a TextTrack via the addCue() method but the text track does not have its text
+    // track kind set to metadata, throw a InvalidNodeTypeError exception and don't add the cue to the TextTrackList

[acolwell GONE FROM CHROMIUM, 2014/04/04 23:25:27]

nit: I think there is a typo in the spec. s/TextTrackList/TextTrackCueList/

+    // of the TextTrack.
+    if (cue->cueType() == TextTrackCue::Data && kind() != metadataKeyword()) {
+        exceptionState.throwDOMException(InvalidNodeTypeError, "DataCues can only be added to tracks with kind='metadata'");

[philipj_slow, 2014/04/04 14:54:33]

The spec does say this, but it doesn't make sense. TextTrack.kind is readonly,
but it can change if the TextTrack is backed by a <track> element, and acolwell
wants to make the attribute readwrite for MSE. Also, is there any code that is
made simpler if DataCue implies kind=metadata? If not it seems the spec should
change.

[Brendan Long, 2014/04/04 15:07:22]

That makes sense. I'll try bring it up on the list again.

[Brendan Long, 2014/04/04 15:17:00]

New bug:

https://www.w3.org/Bugs/Public/show_bug.cgi?id=25261

+        return;
+    }
+
     // TODO(93143): Add spec-compliant behavior for negative time values.
     if (std::isnan(cue->startTime()) || std::isnan(cue->endTime()) || cue->startTime() < 0 || cue->endTime() < 0)
         return;
 
     // 4.8.10.12.5 Text track API
 
     // The addCue(cue) method of TextTrack objects, when invoked, must run the following steps:
 
     // 1. If the given cue is in a text track list of cues, then remove cue from that text track
     // list of cues.
@@ skipping 183 matching lines @@
 {
     return m_document;
 }
 
 HTMLMediaElement* TextTrack::mediaElement()
 {
     return m_trackList ? m_trackList->owner() : 0;
 }
 
 } // namespace WebCore