Ignore <rt> children when determining WebVTT text direction (LTR/RTL)

LayoutTests/media/track/track-cue-rendering-rtl-expected.txt

Index: LayoutTests/media/track/track-cue-rendering-rtl-expected.txt
diff --git a/LayoutTests/media/track/track-cue-rendering-rtl-expected.txt b/LayoutTests/media/track/track-cue-rendering-rtl-expected.txt
index dda40e442544c7cf31786bcf115c9cc7143bc2e3..719657521cbb20afcbd80253e72bb3c1f6eadf1e 100644
--- a/LayoutTests/media/track/track-cue-rendering-rtl-expected.txt
+++ b/LayoutTests/media/track/track-cue-rendering-rtl-expected.txt
@@ -104,5 +104,31 @@ EXPECTED (testCueDisplayBox.innerText == '𝅘𝅥 (Musical symbol quarter note, U+1
 ** The position should be default and CSS direction set to ltr **
 EXPECTED (2 * testCueDisplayBox.offsetLeft == video.videoWidth - testCueDisplayBox.offsetWidth == 'true') OK
 EXPECTED (getComputedStyle(testCueDisplayBox).direction == 'ltr') OK
+
+RUN(video.currentTime = 4.25)
+EVENT(seeked)
+
+** Jump to next cue **
+EXPECTED (video.currentTime == '4.25') OK
+EXPECTED (testTrack.track.activeCues.length == '1') OK
+EXPECTED (testTrack.track.activeCues[0].text == '𝅘𝅥تجربة') OK
+EXPECTED (testCueDisplayBox.innerText == '𝅘𝅥تجربة') OK
+
+** The position should be default and CSS direction set to rtl **
+EXPECTED (2 * testCueDisplayBox.offsetLeft == video.videoWidth - testCueDisplayBox.offsetWidth == 'true') OK
+EXPECTED (getComputedStyle(testCueDisplayBox).direction == 'rtl') OK
+
+RUN(video.currentTime = 4.75)
+EVENT(seeked)
+
+** Jump to next cue **
+EXPECTED (video.currentTime == '4.75') OK
+EXPECTED (testTrack.track.activeCues.length == '1') OK
+EXPECTED (testTrack.track.activeCues[0].text == '1234تجربة') OK
+EXPECTED (testCueDisplayBox.innerText == '1234تجربة') OK
+
+** The position should be default and CSS direction set to ltr **
+EXPECTED (2 * testCueDisplayBox.offsetLeft == video.videoWidth - testCueDisplayBox.offsetWidth == 'true') OK
+EXPECTED (getComputedStyle(testCueDisplayBox).direction == 'ltr') OK
 END OF TEST