Enable WebVTT regions for runtime testing, updated tests and minor fixes

LayoutTests/media/track/regions-webvtt/text-track-region-display-expected.txt

Index: LayoutTests/media/track/regions-webvtt/text-track-region-display-expected.txt
diff --git a/LayoutTests/media/track/regions-webvtt/text-track-region-display-expected.txt b/LayoutTests/media/track/regions-webvtt/text-track-region-display-expected.txt
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index 0000000000000000000000000000000000000000..e6692138b5d8121348479eb98169ad86fd9120be
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+++ b/LayoutTests/media/track/regions-webvtt/text-track-region-display-expected.txt
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+Tests default rendering for TextTrackCues that belong to a TextTrackRegion.
+
+EVENT(canplaythrough)
+** The text track has only one region **
+EXPECTED (testTrack.regions.length == '1') OK
+
+** Inspecting cues displayed within region**
+
+RUN(video.currentTime = 0.2)
+EVENT(seeked)
+Total cues in region: 1
+Cue content is: We are in New York City
+Cue lines visible from this cue: 1
+EXPECTED (totalVisibleLines <= testTrack.regions[0].height == 'true') OK
+
+RUN(video.currentTime = 0.5)
+EVENT(seeked)
+Total cues in region: 2
+Cue content is: We are in New York City
+Cue lines visible from this cue: 1
+Cue content is: Second cue
+Cue lines visible from this cue: 1
+EXPECTED (totalVisibleLines <= testTrack.regions[0].height == 'true') OK
+
+RUN(video.currentTime = 1)
+EVENT(seeked)
+Total cues in region: 3
+Cue content is: We are in New York City
+Cue lines visible from this cue: 0
+Cue content is: Second cue
+Cue lines visible from this cue: 0
+Cue content is: Multiline Cue
+Cue lines visible from this cue: 2
+EXPECTED (totalVisibleLines <= testTrack.regions[0].height == 'true') OK
+
+RUN(video.currentTime = 2.3)
+EVENT(seeked)
+Total cues in region: 2
+Cue content is: Multiline Cue
+Cue lines visible from this cue: 1
+Cue content is: Fourth cue!
+Cue lines visible from this cue: 1
+EXPECTED (totalVisibleLines <= testTrack.regions[0].height == 'true') OK
+
+RUN(video.currentTime = 3)
+EVENT(seeked)
+Total cues in region: 1
+Cue content is: Fourth cue!
+Cue lines visible from this cue: 1
+EXPECTED (totalVisibleLines <= testTrack.regions[0].height == 'true') OK
+END OF TEST
+