Implement DataCue interface.

Source/core/html/track/TextTrack.cpp

Index: Source/core/html/track/TextTrack.cpp
diff --git a/Source/core/html/track/TextTrack.cpp b/Source/core/html/track/TextTrack.cpp
index 5789476a8f848fd66ba5818692bb11e87bcb4c15..ea0f2ebbed28b8915b2f306fb99b7995273c4797 100644
--- a/Source/core/html/track/TextTrack.cpp
+++ b/Source/core/html/track/TextTrack.cpp
@@ -224,13 +224,24 @@ TextTrackCueList* TextTrack::activeCues() const
     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;