bug#36347: 26.2.90; fontification mistakes contraction for a string in HTML

[Mike Kupfer <mkupfer@alum.berkeley.edu>]

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To reproduce:

1. start emacs with -Q
2. Visit (C-x C-f) the attached file (foo.html).

When I do this with 26.2.90, the text starting with the apostrophe in
"doesn't", and ending at the end of file, is fontified as a string.

When I do this with 26.2-rc1, the text is fontified as I would expect
(HTML tags are in blue, everything else is in the default black or dark
gray).


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In GNU Emacs 26.2.90 (build 1, x86_64-pc-linux-gnu, X toolkit, Xaw scroll bars)
 of 2019-06-23 built on alto
Windowing system distributor 'The X.Org Foundation', version 11.0.11902000
System Description:	Debian GNU/Linux 9.9 (stretch)

Recent messages:
Mark set [3 times]
Auto-saving...done
Saving file /home/kupfer/private_html/computers.html...
Wrote /home/kupfer/private_html/computers.html
When done with this frame, type C-x 5 0
GNU Emacs 26.2.90 (build 1, x86_64-pc-linux-gnu, X toolkit, Xaw scroll bars) of 2019-06-23
Quit
When done with this frame, type C-x 5 0
Quit
Mark saved where search started

Configured features:
XPM JPEG TIFF GIF PNG SOUND NOTIFY GNUTLS LIBXML2 FREETYPE LIBOTF XFT
ZLIB TOOLKIT_SCROLL_BARS LUCID X11 XDBE XIM THREADS

Important settings:
  value of $LC_TIME: C
  value of $LANG: en_US.utf8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  shell-dirtrack-mode: t
  delete-selection-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message rmc puny format-spec rfc822 mml
mml-sec password-cache epa derived epg epg-config gnus-util rmail
rmail-loaddefs mm-decode mm-bodies mm-encode mail-parse rfc2231
mailabbrev gmm-utils mailheader sendmail rfc2047 rfc2045 ietf-drums
mm-util mail-prsvr mail-utils dired-x dired dired-loaddefs add-log
skeleton misearch multi-isearch sgml-mode seq gv dom elec-pair server
noutline outline easy-mmode cc-mode cc-fonts cc-guess cc-menus cc-cmds
cc-styles cc-align cc-engine cc-vars cc-defs byte-opt bytecomp
byte-compile cconv shell pcomplete comint ansi-color ring xcscope
easymenu advice delsel vc cl-loaddefs cl-lib vc-dispatcher timeclock
mdk-hacks time-date mule-util tooltip eldoc electric uniquify ediff-hook
vc-hooks lisp-float-type mwheel term/x-win x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
newcomment text-mode elisp-mode lisp-mode prog-mode register page
menu-bar rfn-eshadow isearch timer select scroll-bar mouse jit-lock
font-lock syntax facemenu font-core term/tty-colors frame cl-generic
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite charscript charprop
case-table epa-hook jka-cmpr-hook help simple abbrev obarray minibuffer
cl-preloaded nadvice loaddefs button faces cus-face macroexp files
text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget hashtable-print-readable backquote threads inotify
dynamic-setting font-render-setting x-toolkit x multi-tty
make-network-process emacs)

Memory information:
((conses 16 152389 9893)
 (symbols 48 26251 1)
 (miscs 40 136 313)
 (strings 32 47063 956)
 (string-bytes 1 1299530)
 (vectors 16 20032)
 (vector-slots 8 595254 13062)
 (floats 8 89 321)
 (intervals 56 1199 0)
 (buffers 992 17))