The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/80ccfaf557f5ad07e5de8bcc08e1aba84190b2a0

commit 80ccfaf557f5ad07e5de8bcc08e1aba84190b2a0
Author: Fredrik Söderquist <fs@opera.com>
Date: Mon Sep 04 10:26:17 2017

Support all of HTML's character entities in WebVTT

This updates the VTTTokenizer to align with the updated WebVTT tokenizer
steps:

 https://w3c.github.io/webvtt/#html-character-reference-in-data-state

and

 https://w3c.github.io/webvtt/#html-character-reference-in-annotation-state

The old states for handling "escapes" are removed, adding new ones per
above, for invoking the HTML parser's entity matcher.
A new WEBVTT_SWITCH_TO operation is also added so that state transitions
can be performed without advancing the input position. (Matches
mechanics of the HTML parser.)

The WPT test webvtt/parsing/cue-text-parsing/tests/entities.html is
updated since it had an incorrect expected result for the "&notit;"
case.

Old, now incorrect and/or redundant, tests for entities are removed.

Bug:  761303 
Change-Id: I8ffb4fb2da7169c2ba3c84eb8c3206daabefbb30
Reviewed-on: https://chromium-review.googlesource.com/647586
Reviewed-by: Philip Jägenstedt <foolip@chromium.org>
Commit-Queue: Fredrik Söderquist <fs@opera.com>
Cr-Commit-Position: refs/heads/master@{#499473}
[modify] https://crrev.com/80ccfaf557f5ad07e5de8bcc08e1aba84190b2a0/third_party/WebKit/LayoutTests/external/wpt/webvtt/parsing/cue-text-parsing/dat/entities.dat
[delete] https://crrev.com/fb95760c3981b8df5f339ec635f1229f83c6e573/third_party/WebKit/LayoutTests/external/wpt/webvtt/parsing/cue-text-parsing/tests/entities-expected.txt
[modify] https://crrev.com/80ccfaf557f5ad07e5de8bcc08e1aba84190b2a0/third_party/WebKit/LayoutTests/external/wpt/webvtt/parsing/cue-text-parsing/tests/entities.html
[delete] https://crrev.com/fb95760c3981b8df5f339ec635f1229f83c6e573/third_party/WebKit/LayoutTests/media/track/opera/track/webvtt/parsing-cue-data/dat/entities.dat
[delete] https://crrev.com/fb95760c3981b8df5f339ec635f1229f83c6e573/third_party/WebKit/LayoutTests/media/track/opera/track/webvtt/parsing-cue-data/tests/entities.html
[modify] https://crrev.com/80ccfaf557f5ad07e5de8bcc08e1aba84190b2a0/third_party/WebKit/Source/core/html/track/vtt/VTTTokenizer.cpp