MSE: Implement TrackDefault object

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 b95a35dbef448af17805b09669f465e226735144..67c9d5a1b8c286125d0f7e2afe232ab21730a112 100644
--- a/Source/core/html/track/TextTrack.cpp
+++ b/Source/core/html/track/TextTrack.cpp
@@ -141,6 +141,22 @@ bool TextTrack::isValidKindKeyword(const AtomicString& value)
     return false;
 }
 
+bool TextTrack::isValidKindKeyword(const String& value)

[philipj_slow, 2014/11/14 12:03:37]

AtomicString is free to convert to String (and has an implicit cast operator) so
only the String variant is needed. (I hope, I only tested the AudioTrack case.)

[wolenetz, 2014/11/17 21:51:07]

Done.

+{
+    if (value == subtitlesKeyword())
+        return true;
+    if (value == captionsKeyword())
+        return true;
+    if (value == descriptionsKeyword())
+        return true;
+    if (value == chaptersKeyword())
+        return true;
+    if (value == metadataKeyword())
+        return true;
+
+    return false;
+}
+
 void TextTrack::setTrackList(TextTrackList* trackList)
 {
     if (!trackList && mediaElement() && m_cues)