Issue #2502785 by dawehner, effulgentsia, tim.plunkett, amateescu, Fabianx, Wim Leers, catch, dsnopek, EclipseGc, yched, Berdir, larowlan, mondrake, olli: Remove support for $form_state->setCached() for GET requests

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files

Issue #2263569 by tim.plunkett, effulgentsia, Fabianx, dawehner, Wim Leers, larowlan: Bypass form caching by default for forms using #ajax.

Issue #2368797 by Wim Leers, dawehner, rteijeiro: Optimize ajaxPageState to keep Drupal 8 sites fast on high-latency networks, prevent CSS/JS aggregation from taking down sites and use HTTP GET for AJAX requests

Issue #2378095 by Wim Leers, Devin Carlson: Convert all remaining attached individual CSS/JS assets to attached asset libraries

Issue #2363139 by Wim Leers, dawehner, larowlan: _content controllers may only return render arrays, not strings.

Issue #2335659 by tim.plunkett, dawehner, effulgentsia, sun: Remove FormState ArrayAccess usage from core.

Issue #2273277 by Wim Leers, effulgentsia, Fabianx: Fixed Figure out a solution for the problematic interaction between the render system and the theme system when using #pre_render.

Issue #2147009 by tim.plunkett, RoSk0 | vijaycs85: Convert all forms in ajax_forms_test module to FormInterface.

Issue #2121175 by Codenator, tim.plunkett, cosmicdreams, jayeshanandani, grom358, ianthomas_uk, Xano: Remove usage of drupal_get_form().

Issue #2095335 by Wim Leers, vijaycs85: Remove drupal_add_css() and drupal_add_js() from the ajax system.

Issue #2074509 by tim.plunkett, falcon03, mgifford, Xano: Fixed Add missing #title property to ensure form accessibility.

Issue #1987602 by glennpratt, juampy, pwieck, vijaycs85, dawehner, tim.plunkett, effulgentsia: Convert ajax_form_callback() to a new style controller.

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

Issue #1848880 by Wim Leers, effulgentsia: Test order of AJAX commands: add Ajax\FrameworkTest::testOrder(), strengthen testLazyLoad(), fix JS settings not being prepended.

Issue #1356170 by ohnobinki, tim.plunkett: Remove all uses of array_merge_recursive(), or document why they are being used instead of NestedArray::mergeDeep().

Issue #1802072 by fubhy, Stalski: Ajax callbacks should be callbacks defined as function or class method.

Issue #1431658 by Albert Volkman, xjm, kid_icarus, ChinggizKhan, rgristroph, connork: Massive API docs cleanup for system tests

Issue #1754712 by TravisCarden, Bußmeyer, pingers: Fixed @return unknown_type() should be @return mixed.

Issue #1071818 by JeremyFrench, nod_, reglogge, anthbel, xjm, sun, NROTC_Webmaster, lliss, Cottser: Fixed Lazy-loading CSS fails in IE.