Handle recovery on "timestamp-looking" lines in the WebVTT parser

Handle recovery on "timestamp-looking" lines in the WebVTT parser
https://bugs.webkit.org/show_bug.cgi?id=130610

Reviewed by Eric Carlson.

Merged from Blink (patch by fs@opera.com):
https://chromium.googlesource.com/chromium/blink/+/b669a380efbffe25f3b154b026b57b9822ce08e2
http://crbug.com/75273002

Source/WebCore:

Tests: media/track/track-webvtt-tc031-cue-recovery.html
       media/track/track-webvtt-tc032-degenerate-cues.html

* html/track/WebVTTParser.cpp:
(WebCore::WebVTTParser::parse):
(WebCore::WebVTTParser::collectCueText):
(WebCore::WebVTTParser::recoverCue):
(WebCore::WebVTTParser::ignoreBadCue):
* html/track/WebVTTParser.h:

LayoutTests:

* media/track/captions-webvtt/tc006-cue-id-error.vtt:
* media/track/captions-webvtt/tc007-cue-no-id-error.vtt:
* media/track/captions-webvtt/tc011-cues-no-separation.vtt:
* media/track/captions-webvtt/tc031-cue-recovery-cuetext.vtt: Added.
* media/track/captions-webvtt/tc031-cue-recovery-header.vtt: Added.
* media/track/captions-webvtt/tc031-cue-recovery-note.vtt: Added.
* media/track/captions-webvtt/tc032-degenerate-cues.vtt: Added.
* media/track/track-webvtt-tc006-cue-identifiers-expected.txt:
* media/track/track-webvtt-tc006-cue-identifiers.html:
* media/track/track-webvtt-tc007-cue-no-id-expected.txt:
* media/track/track-webvtt-tc007-cue-no-id.html:
* media/track/track-webvtt-tc011-blank-lines-expected.txt:
* media/track/track-webvtt-tc011-blank-lines.html:
* media/track/track-webvtt-tc031-cue-recovery-expected.txt: Added.
* media/track/track-webvtt-tc031-cue-recovery.html: Added.
* media/track/track-webvtt-tc032-degenerate-cues-expected.txt: Added.
* media/track/track-webvtt-tc032-degenerate-cues.html: Added.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@166080 268f45cc-cd09-0410-ab3c-d52691b4dbfc