Issue #2476947 by mdrummond, Wim Leers, davidhernandez, lauriii, joelpittet, andypost, Cottser, JeroenT, Manuel Garcia, rpayanm: Convert "title" page element into a block

Issue #2569083 by dsnopek, tim.plunkett, Wim Leers: Allow passing cacheable metadata to display variants (to enable Panels Everywhere)

Issue #2550941 by dsnopek, tim.plunkett, lslinnet: Allow passing contexts to display variants (to enable Panels Everywhere to use static context and relationships)

Issue #2551989 by Wim Leers, Crell: Move replacing of placeholders from HtmlRenderer to HtmlResponseAttachmentsProcessor

Issue #2512062 by dsnopek, tim.plunkett, Wim Leers: VariantInterface extends ConfigurablePluginInterface so PageDisplayVariantSelectionEvent should allow passing configuration to the Variant (to enable Panels Everywhere)

Issue #2505989 by alexpott, dawehner, olli: Controllers render caching at the top level and setting a custom page title lose the title on render cache hits

Issue #2450993 by Wim Leers, Fabianx, Crell, dawehner, effulgentsia: Rendered Cache Metadata created during the main controller request gets lost

Issue #2407195 by Wim Leers, Fabianx, joelpittet, lauriii, Crell: Move attachment processing to services and per-type response subclasses

Issue #2497259 by catch, tim.plunkett, alexpott: system_region_list() unnecessarily translates region names

Issue #2478483 by Wim Leers, Fabianx: Introduce placeholders (#lazy_builder) to replace #post_render_cache

Issue #2477461 by borisson_, googletorp, Wim Leers, Crell: Move X-Generator header to its own listener

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 #2463009 by Wim Leers: Introduce CacheableResponseInterface: consolidate ways of setting X-Drupal-Cache-Tags/Contexts headers

Issue #2466585 by Wim Leers, Fabianx: Decouple cache implementation from the renderer and expose as renderCache service

Issue #2468151 by lhangea, rpayanm, Palashvijay4O: Rename the CacheContexts service to CacheContextsManager

Issue #2467041 by mr.baileys, jan.stoeckler: max-age on HTML responses wrongly set to `max-age=0, private` instead of `max-age=N, public` (breaks reverse proxies and client-side caching)

Issue #2226621 by JeroenT, ianthomas_uk, lokapujya, pjonckiere, marcingy, LinL, Xano, rpayanm, piyuesh23: Remove usage of element_info(), element_child() and element_children(). Deprecate element_info_property()

Issue #2432837 by Wim Leers, Fabianx: Make cache contexts hierarchical (e.g. 'user' is more specific than 'user.roles')

Issue #2443073 by Wim Leers, joshtaylor: Add #cache[max-age] to disable caching and bubble the max-age

Issue #2350551 by Wim Leers, alexpott, damiankloip, arlinsandbulte: Views fields that have attached assets are lost when Views output caching is enabled

Issue #2379741 by Wim Leers, damiankloip: Add Renderer::getCacheableRenderArray() to encapsulate which data is needed for caching a render array and have views use it

Issue #2346937 by dawehner, larowlan, Wim Leers, claudiu.cristea, msonnabaum: Implement a Renderer service; reduces drupal_render / _theme service container calls