Issue #2506195 by alexpott, joelpittet, xjm, David_Rothstein, Fabianx, pwolanin: Remove SafeMarkup::set() from Xss::filter()

Issue #2511472 by Wim Leers, Fabianx, dawehner: Refactor all usages of drupal_render()/Renderer::render() that break #2450993

Issue #2315791 by alexpott, cilefen, dawehner: Add functionality to open results in browser window to run-tests.sh

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

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

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

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

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 #697760 by sun: Replace getInfo() in tests with native phpDoc + annotations (following PHPUnit).

Issue #2234159 by alexpott: Fixed config importing through the UI and change ConfigImportAll test using the UI.

Issue #2207767 by temaruk, Coornail, rteijeiro, alexrayu, LewisNyman: Replace watchdog icons with Libricons.

Issue #2171071 by jessebeach, dawehner, chakrapani, longwave, Gábor Hojtsy, xjm, Wim Leers: Rename drupal_add_library() to _drupal_add_library() and remove its uses.

Issue #2140505 by amateescu, tim.plunkett: Re-running a simpletest no longer displays the batch progress or duration.

Issue #2028939 by cilefen, deekayen: Clean up line wrapping in simpletest documentation and make namespaces in docs fully qualified

Issue #2009670 by esunger, jeroen12345, hussainweb: Replace theme() with drupal_render() in simpletest module.

Issue #1668866 by ParisLiakos, aspilicious, tim.plunkett, pdrake, g.oechsler, dawehner, Berdir, corvus_ch, damiankloip, disasm, marcingy, neclimdul: Replace drupal_goto() with RedirectResponse.

Issue #1998140 by dawehner, ParisLiakos, tim.plunkett: Remove backward compatible ControllerInterface.

Issue #1987066 followup by swentel: [Hotfix] Change notice: Rename files to match CSS file naming convention.

This reverts commit c4e52bb6.