Issue #2367747 by Palashvijay4O, andypost, Alienpruts, Cottser, er.pushpinderrana, gaurav.pahuja, pfrenssen, rpayanm, vadim.hirbu: Remove usage of system_rebuild_theme_data()

Issue #2151469 by rpayanm, lokapujya, JeroenT, alansaviolobo, Richard Damon, pflame, ianthomas_uk: Clean-up usage of deprecated list_themes() and _system_rebuild_theme_data() in favor of theme_handler service.

Issue #1885788 by alimac, tim.plunkett | jenlampton: Fixed An AJAX HTTP error occurred during module installation via UI.

Issue #2215543 by Antti J. Salminen, mrjmd, alexrayu, olemedia | joelpittet: Replace strong tag with CSS in template_preprocess_authorize_report and remove id..

Issue #1825952 by Fabianx, joelpittet, bdragon, heddn, chx, xjm, pwolanin, mikey_p, ti2m, bfr, dags, cilefen, scor, mgifford: Turn on twig autoescape by default

Issue #1067408 by alexpott, Jalandhar, jessebeach, Désiré, neetu morwani, dawehner, sun: Themes do not have an installation status.

Revert "Issue #2218039 by sun, dawehner: Render the maintenance/install page like any other HTML page."

Broke update.php.

This reverts commit 10b03890.

Issue #2169765 by philipz, Sutharsan, ckrina, c_lehel, LewisNyman: Redesign update.php to be more consistent with the installation process.

Revert "Issue #2169765 by philipz, Sutharsan, ckrina, c_lehel, LewisNyman: Redesign update.php to be more consistent with the installation process."

This reverts commit 728aad1d.

Issue #2169765 by philipz, Sutharsan, ckrina, c_lehel, LewisNyman: Redesign update.php to be more consistent with the installation process.

Issue #340723 by ParisLiakos, sun, Berdir, glennpratt, Cottser, swentel, alexpott, tstoeckler, Xano, tim.plunkett, BassistJimmyJam | beejeebus: Make modules and installation profiles only require .info.yml files.

Revert "Issue #340723 by ParisLiakos, sun, Berdir, glennpratt, Cottser, swentel, tstoeckler, Xano, tim.plunkett, BassistJimmyJam: Make modules and installation profiles only require .info.yml files."

This reverts commit b4c561d0.

Issue #340723 by ParisLiakos, sun, Berdir, glennpratt, Cottser, swentel, tstoeckler, Xano, tim.plunkett, BassistJimmyJam: Make modules and installation profiles only require .info.yml files.

Issue #1351352 by sun, lucascaro, Gábor Hojtsy, rupertj: Distribution installation profiles are no longer able to override the early installer screens.

Issue #2045927 by herom, martin107, ianthomas_uk, Xano, michaellander, Sutharsan: Replace all drupal_alter() deprecated function calls.

Issue #2167109 by Berdir, sun, alexpott, ACF, acrollet, adamdicarlo, Albert Volkman, andreiashu, andyceo, andypost, anenkov, aspilicious, barbun, beejeebus, boombatower, cam8001, chriscalip, chx, cosmicdreams, dagmar, damiankloip, dawehner, deviance, disasm, dixon_, dstol, ebrowet, Gábor Hojtsy, heyrocker, Hydra, ianthomas_uk, japicoder, jcisio, jibran, julien, justafish, jvns, KarenS, kbasarab, kim.pepper, larowlan, Lars Toomre, leschekfm, Letharion, LinL, lirantal, Lukas von Blarer, marcingy, Mike Wacker, mrf, mtift, mtunay, n3or, nadavoid, nick_schuch, Niklas Fiekas, ParisLiakos, pcambra, penyaskito, pfrenssen, plopesc, Pol, Rok Žlender, rvilar, swentel, tim.plunkett, tobiasb, tsvenson, typhonius, vasi1186, vijaycs85, wamilton, webchick, webflo, wizonesolutions, xjm, yched, YesCT, znerol: Remove Variable subsystem.

Issue #2008270 by typhonius, mcjim, Wim Leers, vijaycs85, mr.baileys, JohnAlbin: Remove drupal_add_css() from template_preprocess_maintenance_page() — use #attached.

Issue #1886448 by dawehner, sun, Berdir, ParisLiakos: Rewrite the theme registry into a proper service.

Issue #1829170 by LinL, socketwench, vijaycs85, mtift, LittleCoding, andypost, dawehner, ianmthomasuk: Convert the Maintenance Theme variable to settings.

Issue #1839318 by JohnAlbin, echoz: Added Replace drupal.base.css library with normalize.css for all themes.

Issue #2008270 by mcjim, typhonius: Remove drupal_add_css() from _drupal_maintenance_theme() — use #attached.

Issue #1924430 by echoz, JohnAlbin, izus, kim.pepper, LewisNyman: Add drupal.base library for base CSS styles.

Issue #1337554 by LewisNyman, Bojhan, YesCT, Cottser, jenlampton, Xano, David_Rothstein, larowlan, nilnullvoid: Develop and use separate branding for the installer.

Issue #2023093 by nguerrero, ggiammi, penyaskito: Fix reference to obsolete function in code comment

Issue #1363112 by mparker17, mgifford, tlattimore, Jacine, dcmouyard, bowersox, ry5n, ahdiaz: Simplify names of 'element-x' helper classes.

Issue #1987066 by Kevin Morse, JohnAlbin, rteijeiro, echoz, ry5n: Rename files to match CSS file naming convention.

Issue #1957154 by joates, ayelet_Cr, xjm | Berdir: Replace calls to drupal_container()->get('module_handler()') service with Drupal::moduleHandler().