Issue #1305882 by dawehner, nod_, Fabianx, Steven Jones, sun, nlisgo: drupal_html_id() considered harmful; remove ajax_html_ids to use GET (not POST) AJAX requests

Issue #2457887 by prateekMehta, stefan.r, rpayanm, alexpott: Use Utility\SafeMarkup class instead of Utility\String for placeholder(), checkPlain(),format() functions

Issue #2252763 by damiankloip, skipyT, martin107, dawehner, dashaforbes: Views exposed filter form causes enormous form state cache entries

Issue #2407361 by cilefen, JeroenT, hussainweb, neclimdul, ircmaxell, tim.plunkett, nlisgo, Crell: Move usages of drupal_html_id() to Html::getUniqueId()

Revert "Issue #2407361 by JeroenT, cilefen, hussainweb: Move usages of drupal_html_id() to Html::getUniqueId()"

This reverts commit 85b8c837.

Issue #2407361 by JeroenT, cilefen, hussainweb: Move usages of drupal_html_id() to Html::getUniqueId()

Issue #2409209 by dawehner, xjm, mpdonadio, Wim Leers, hussainweb, RavindraSingh, prashantgoel: Replace all _url() calls beside the one in _l()

Issue #2333719 by alvar0hurtad0, idebr, LewisNyman, msankhala: Abstract Views Exposed Form styling out into a reusable class

Issue #2382543 by rpayanm, ianthomas_uk: Remove usage of drupal_html_class() and drupal_clean_css_identifier()

Issue #2343661 by larowlan, tim.plunkett | xjm: Rename l() to _l() and url() to _url(), and document replacements.

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

Issue #2318281 by tim.plunkett, dawehner | kim.pepper: Provide a standard way to check a plugin is an instance of the required interface.