Issue #2667242 by Anul, felribeiro, eojthebrave, pranavbabbar: Use consistent terminology when referencing administration themes in the UI (not "admin theme")

Issue #2665992 by alexpott, klausi, heykarthikwithu, xjm, tstoeckler: @file is not required for classes, interfaces and traits

Issue #304540 by typhonius, BrockBoland, nabiyllin, RobLoach, marcingy, ravi.khetri, jyotisankar, sudhanshug, jaredsmith, nesta_: Disable themes when theme engine or base theme aren't available

Issue #2570355 by Sutharsan, stefan.r, kgoel, josephdpurcell, joelpittet, justAChris, dawehner, pfrenssen, pwolanin, David_Rothstein, catch: Replace remaining !placeholder and @placeholder with :placeholder for URLs

Issue #2568607 by alexpott, dawehner: Replace remaining !placeholder for Non-URL HTML outputs only in Theme name stuff in SystemController

Issue #2489830 by cilefen, davidhernandez, dcmul, Adam Clarey, joshi.rohit100, rpayanm, sqndr, Cottser, lauriii: Improve theme compatibility error message

Issue #1805054 by Wim Leers, Gábor Hojtsy, effulgentsia, jibran, jessebeach, catch, dawehner, Fabianx, sun, larowlan: Cache localized, access filtered, URL resolved, and rendered menu trees

Issue #2478443 by Wim Leers: Set the 'is-active' class for anonymous users in a Response Filter instead of a #post_render_cache callback

Issue #2031641 by aburrows, lauriii, nlisgo, Pol, redsquid, tuutti, LewisNyman, akalata, agviu, kallehauge, _nolocation, rpayanm, saki007ster, mdrummond, RavindraSingh, brahmjeet789: Change active class to is-active

Issue #2403301 by lokapujya, penyaskito, Wim Leers: Menu item "active" class is not correctly added when using a view as the frontpage

Issue #2412241 by idebr, Wim Leers: Active menu links with identical paths get a duplicate "active" class for every active menu link

Issue #2347465 by tim.plunkett, dawehner, cilefen: Convert all instances of #type link/links to convert to use routes.

Issue #2329851 by lanchez, lauriii, Jolidog | davidhernandez: Move miscellaneous system classes from preprocess to templates.

Issue #2340251 by iMiksu, alexpott, tim.plunkett, dawehner, Wim Leers: Remove most remaining url() calls.

Issue #2305707 by cilefen, pwolanin, dawehner, LinL: MenuLinkContent disabled field should be renamed to enabled and use positive logic.

Issue #2301317 by pwolanin, dawehner, Wim Leers, effulgentsia, YesCT, xjm, alexpott: MenuLinkNG part4: Conversion.

Revert "Issue #2301317 by pwolanin, effulgentsia, Wim Leers, dawehner, alexpott: MenuLinkNG part4: Conversion."

This reverts commit fd2db9cd.

Issue #2301317 by pwolanin, effulgentsia, Wim Leers, dawehner, alexpott: MenuLinkNG part4: Conversion.

Issue #2079797 by ParisLiakos, Xano, amateescu, tim.plunkett: Provide a trait for $this->t() and $this->formatPlural().

Issue #2243549 by agerson, cs_shadow | jhodgdon: Text changes needed as follow-up to Menu UI module rename.

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

Issue #2208609 by sun, Jalandhar, damiankloip: Move Json utility class into Drupal\Component\Serialization.

Issue #1987848 by disasm, ocsilalala, kim.pepper, pwieck, Cottser, pratik60, h3rj4n, pfrenssen, InternetDevels, ParisLiakos, rgoodine, tlyngej, vijaycs85, robeano: Convert system_theme_default() to a new style controller.

Issue #2151089 by longwave, joelpittet, c4rl, IshaDakota, pplantinga, gnuget, jeanfei, sbudker1, Cottser: Convert theme_admin_block() to Twig.

Issue #2210197 by sun, longwave, Sutharsan: Remove public access to Extension::$type, ::$name, ::$filename.

Revert "Issue #2210197 by sun, longwave: Remove public access to Extension::$type, ::$name, ::$filename." Broke 'drush en simpletest' on testbots

This reverts commit 2c51074d.

Issue #2110501 by tim.plunkett, pwolanin, tstoeckler: ControllerBase should implement ContainerInjectionInterface like FormBase.

Issue #1979468 by Wim Leers, nod_, pwolanin, longwave, thedavidmeister, jessebeach, larowlan | catch: .active from linkGenerator(), l() and theme_links() forces an upper limit of per-page caching for all content containing links.

Issue #1987854 by splatio, disasm, kim.pepper, vijaycs85, sidharthap, dawehner: Convert system_themes_page() to a new style controller.

Revert "Issue #1979468 by Wim Leers, pwolanin, nod_, thedavidmeister, larowlan: .active from linkGenerator(), l() and theme_links() forces an upper limit of per-page caching for all content containing links."

This reverts commit 624296e7.

Issue #1979468 by Wim Leers, pwolanin, nod_, thedavidmeister, larowlan: .active from linkGenerator(), l() and theme_links() forces an upper limit of per-page caching for all content containing links.