bug#40685: 28.0.50; eww browser chews up 100% cpu when displaying looping gif animations

[Francis Meetze <francis@bridgesense.com>]

When opening a web page in the Emacs browser that contains infinite looping gif animations Emacs starts spinning up 100% CPU even after the emacs browser is closed.  Emacs has to be completely shut down to reduce the CPU usuage.

If the 100% CPU process is allowed to run its course, it eventually stops after several minutes with the message, "Stopping animation; animation possibly too big". 
    

In GNU Emacs 28.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.24.13, cairo version 1.16.0)
 of 2020-04-16 built on localhost.localdomain
Repository revision: d5a7df8c02f04102d50a5cd2290262f59f2b1415
Repository branch: master
Windowing system distributor 'Fedora Project', version 11.0.12006000
System Description: Fedora 31 (Thirty One)

Recent messages:
ad-handle-definition: ‘vc-revert’ got redefined
BBDB: sendmail insinuation deprecated.  Use mail.
Loading /home/francis/.emacs.d/recentf...done
Cleaning up the recentf list...done (0 removed)
Turning on magit-auto-revert-mode...done
For information about GNU Emacs and the GNU system, type C-h C-a.
Package cl is deprecated
Contacting host: bridgesense.com:443
ad-handle-definition: ‘open-network-stream’ got redefined
uncompressing publicsuffix.txt.gz...done

Configured using:
 'configure --without-makeinfo --with-gnutls=ifavailable
 --with-mailutils'

Configured features:
XPM JPEG TIFF GIF PNG CAIRO SOUND DBUS GSETTINGS GLIB NOTIFY INOTIFY
LIBSELINUX GNUTLS LIBXML2 FREETYPE HARFBUZZ M17N_FLT LIBOTF ZLIB
TOOLKIT_SCROLL_BARS GTK3 X11 XDBE XIM MODULES THREADS PDUMPER GMP

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

Major mode: Dashboard

Minor modes in effect:
  general-override-mode: t
  global-auto-complete-mode: t
  global-magit-file-mode: t
  magit-auto-revert-mode: t
  global-git-commit-mode: t
  ranger-override-dired-mode: t
  recentf-mode: t
  page-break-lines-mode: t
  fancy-battery-mode: t
  global-git-gutter-mode: t
  which-key-mode: t
  yas-global-mode: t
  yas-minor-mode: t
  csv-field-index-mode: t
  projectile-mode: t
  smooth-scrolling-mode: t
  global-flycheck-mode: t
  autopair-global-mode: t
  show-paren-mode: t
  ivy-mode: t
  helm-mode: t
  async-bytecomp-package-mode: t
  helm--remap-mouse-mode: t
  evil-commentary-mode: t
  global-evil-surround-mode: t
  evil-surround-mode: t
  global-evil-matchit-mode: t
  evil-matchit-mode: t
  global-undo-tree-mode: t
  undo-tree-mode: t
  shell-dirtrack-mode: t
  evil-mode: t
  evil-local-mode: t
  override-global-mode: t
  save-place-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Load-path shadows:
None found.

Features:
(shadow bbdb-message mail-extr emacsbug sendmail helm-command helm-elisp
helm-eval edebug backtrace helm-info jka-compr gnutls network-stream
url-cache winner whitespace magit-bookmark bookmark pp general
counsel-bbdb ac-html-bootstrap web-completion-data auto-complete-config
ac-php auto-complete ac-php-core popup xcscope f bbdb-vcard vcard
bbdb-mua bbdb-com bbdb bbdb-site timezone evil-magit helm-ls-git vc-git
vc vc-dispatcher magit-submodule magit-obsolete magit-blame magit-stash
magit-reflog magit-bisect magit-push magit-pull magit-fetch magit-clone
magit-remote magit-commit magit-sequence magit-notes magit-worktree
magit-tag magit-merge magit-branch magit-reset magit-files magit-refs
magit-status magit magit-repos magit-apply magit-wip magit-log
which-func magit-diff smerge-mode diff-mode magit-core magit-autorevert
magit-margin magit-transient magit-process magit-mode git-commit
transient magit-git magit-section magit-utils crm log-edit message
rfc822 mml mml-sec mm-decode mm-bodies mm-encode mailabbrev gmm-utils
mailheader pcvs-util with-editor server ranger autorevert filenotify
hl-line dired dired-loaddefs geben dbgp dashboard dashboard-widgets time
recentf tree-widget page-break-lines helm-ag helm-projectile pcase
spaceline-config spaceline-segments spaceline powerline
powerline-separators powerline-themes fancy-battery battery dbus
synosaurus define-word rng-nxml rng-valid rng-loc rng-uri rng-parse
nxml-parse rng-match rng-dt rng-util rng-pttrn nxml-ns nxml-mode
nxml-outln nxml-rap nxml-util nxml-enc xmltok url-http url-auth
mail-parse rfc2231 url-gw nsm rmc helm-flyspell ace-jump-mode cl
linum-relative linum display-line-numbers helm-tramp helm-swoop
gruvbox-dark-soft-theme gruvbox-theme gruvbox autothemer
git-gutter-fringe git-gutter fringe-helper which-key web-beautify
php-scratch s yasnippet rainbow-mode flycheck-color-mode-line face-remap
json-mode json-reformat json-snatcher csv-mode sort sass-mode haml-mode
js css-mode sgml-mode eww mm-url gnus nnheader gnus-util rmail
rmail-loaddefs rfc2047 rfc2045 ietf-drums mail-utils wid-edit mm-util
mail-prsvr url-queue url url-proxy url-privacy url-expand url-methods
url-history mailcap shr text-property-search url-cookie url-domsuf
url-util puny svg dom ruby-mode smie coffee-mode php-mode mode-local
imenu speedbar ezimage dframe etags fileloop generator xref project
add-log cc-langs cc-mode cc-fonts cc-guess cc-menus cc-cmds cc-styles
cc-align cc-engine cc-vars cc-defs php-face php php-project projectile
grep ibuf-ext ibuffer ibuffer-loaddefs flymake-proc flymake compile
warnings xah-css-mode ido web-mode aggressive-indent smooth-scrolling
tramp tramp-loaddefs trampver tramp-integration files-x tramp-compat
parse-time iso8601 ls-lisp exec-path-from-shell multi-term term
disp-table ehelp ob-plantuml flycheck-plantuml flycheck plantuml-mode
xml dash org-bullets epa-file epa derived epg epg-config org-crypt org
ob ob-tangle ob-ref ob-lob ob-table ob-exp org-macro org-footnote
org-src ob-comint org-pcomplete org-list org-faces org-entities
time-date noutline outline org-version ob-emacs-lisp ob-core ob-eval
org-table ol org-keys org-compat org-macs org-loaddefs find-func
cal-menu calendar cal-loaddefs autopair paren swiper ivy delsel colir
color ivy-overlay helm-mode helm-files helm-buffers helm-occur helm-tags
helm-locate helm-grep helm-regexp format-spec helm-utils helm-help
helm-types helm-config helm-easymenu async-bytecomp helm helm-source
eieio-compat helm-multi-match helm-lib async evil-commentary
evil-commentary-integration evil-tutor evil-surround evil-matchit
evil-matchit-sdk evil evil-keybindings evil-integration undo-tree diff
evil-maps evil-commands reveal flyspell ispell evil-jumps
evil-command-window evil-types evil-search evil-ex shell pcomplete
comint ansi-color evil-macros evil-repeat evil-states evil-core advice
evil-common windmove thingatpt rect evil-digraphs evil-vars ring
diminish cl-extra help-mode use-package use-package-ensure
use-package-delight use-package-diminish use-package-bind-key bind-key
easy-mmode use-package-core finder-inf edmacro kmacro saveplace rx info
package easymenu browse-url url-handlers url-parse auth-source cl-seq
eieio eieio-core cl-macs eieio-loaddefs password-cache json subr-x map
url-vars seq byte-opt gv bytecomp byte-compile cconv cl-loaddefs cl-lib
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 tab-bar menu-bar rfn-eshadow isearch
timer select scroll-bar mouse jit-lock font-lock syntax facemenu
font-core term/tty-colors frame minibuffer 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
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 dbusbind
inotify dynamic-setting system-font-setting font-render-setting cairo
move-toolbar gtk x-toolkit x multi-tty make-network-process emacs)

Memory information:
((conses 16 658790 47463)
 (symbols 48 53176 2)
 (strings 32 212837 9154)
 (string-bytes 1 7430431)
 (vectors 16 83039)
 (vector-slots 8 923611 44954)
 (floats 8 566 1005)
 (intervals 56 2849 206)
 (buffers 992 16))