Implement automatic text track selection for 'metadata' tracks

Source/core/html/HTMLMediaElement.cpp

Index: Source/core/html/HTMLMediaElement.cpp
diff --git a/Source/core/html/HTMLMediaElement.cpp b/Source/core/html/HTMLMediaElement.cpp
index 55fe318b23eea679d5f2c41fd8234f17eb74664d..ea4113d068cd8584f5c16240c5bfd92e5ecc7c68 100644
--- a/Source/core/html/HTMLMediaElement.cpp
+++ b/Source/core/html/HTMLMediaElement.cpp
@@ -2924,6 +2924,25 @@ void HTMLMediaElement::configureTextTrackGroup(const TrackGroup& group)
         trackToEnable->setMode(TextTrack::showingKeyword());
 }
 
+void HTMLMediaElement::configureMetadataTextTrackGroup(const TrackGroup& group)
+{
+    ASSERT(group.tracks.size());
+
+    // https://html.spec.whatwg.org/multipage/embedded-content.html#honor-user-preferences-for-automatic-text-track-selection
+
+    // 4. If there are any text tracks in the media element's list of text
+    // tracks whose text track kind is metadata that correspond to track
+    // elements with a default attribute set whose text track mode is set to
+    // disabled, then set the text track mode of all such tracks to hidden
+    for (auto& textTrack : group.tracks) {
+        if (textTrack->mode() != TextTrack::disabledKeyword())
+            continue;
+        if (!textTrack->isDefault())
+            continue;
+        textTrack->setMode(TextTrack::hiddenKeyword());
+    }
+}
+
 void HTMLMediaElement::configureTextTracks()
 {
     TrackGroup captionAndSubtitleTracks(TrackGroup::CaptionsAndSubtitles);
@@ -2979,7 +2998,7 @@ void HTMLMediaElement::configureTextTracks()
     if (chapterTracks.tracks.size())
         configureTextTrackGroup(chapterTracks);
     if (metadataTracks.tracks.size())
-        configureTextTrackGroup(metadataTracks);
+        configureMetadataTextTrackGroup(metadataTracks);
     if (otherTracks.tracks.size())
         configureTextTrackGroup(otherTracks);

[philipj_slow, 2015/01/29 10:34:52]

This looks like it's not per spec if you want to remove it in another CL.
There's also some renaming to be done that would make all of this more
spec-like.

[fs, 2015/01/29 12:05:51]

Yes, I noticed this as well, and I wondered what tracks would be "other"...
replacing it with a ASSERT_NOT_REACHED above ought to do it...