Issue #2935256 by Jo Fitzgerald, voleger, kim.pepper, ibustos, Yogesh Pawar, catch, jibran: Remove all usages of drupal_get_message and drupal_set_message in modules

Issue #2216161 by Wim Leers, alexpott, jhedstrom, borisson_, Berdir: Simplify performance settings page

Issue #2873696 by nvexler, wengerk, gido, Jo Fitzgerald, xjm: Add @internal to core classes, methods, properties to Form Classes

Issue #2892179 by Wim Leers, Berdir: Follow-up for #2775381: clearing render cache in PerformanceForm::submitForm() is obsolete

Issue #2776975 by joelpittet, dawehner, tim.plunkett, xjm, pfrenssen: March 3, 2017: Convert core to array syntax coding standards for Drupal 8.3.x RC phase

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

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 #2383871 by mgifford, rpayanm, a_thakur, maximpodorov, AohRveTPV, jhodgdon: Spellchecking Drupal - PHP

Issue #2368987 by Wim Leers, Berdir, Schnitzel, epari.siva, bircher, vijaycs85, likin: Move internal page caching to a module to avoid relying on config get on runtime

Issue #2392319 by alexpott, effulgentsia: Config objects (but not config entities) should by default be immutable

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

Issue #1182850 by xjm, Stefan Lehmann, jmcintyre, Bojhan: Remove full stops at the end of checkbox options.

Issue #2309323 by Berdir, tim.plunkett: Allow #submit and #validate to be specified as methods of the form object.

Issue #2307419 by Wim Leers: AssetCollectionOptimizerInterface should allow listing and deleting all aggregates (optimized collection assets).

Issue #2149197 by penyaskito, mikey_p, vijaycs85, herom: Replace format_interval with \Drupal::service('date')->formatInterval().

Issue #2239065 by tim.plunkett | webchick: Overridden config bleeding through to configuration forms.

Issue #2158003 by Wim Leers, msonnabaum, effulgentsia, moshe weitzman: Remove Block Cache API in favor of blocks returning #cache with cache tags.

Issue #2203407 by nod_, sun: Replace #attached library array values with provider-namespaced strings.

Issue #2098119 by beejeebus, alexpott, chx: Replace config context system with baked-in locale support and single-event based overrides.

Issue #2080019 by mrsinguyen: Remove Unused local variable $js_hide from /core/modules/system/lib/Drupal/system/Form/PerformanceForm.php.

Issue #2089627 by tim.plunkett: Move \Drupal\system\SystemConfigFormBase to \Drupal\Core\Form\ConfigFormBase.

Issue #1981368 by tim.plunkett, Crell, webchick: Convert all routes to 'module_name().foo_bar()' naming convention.

Issue #1925660 by ACF, tim.plunkett, mtift, heddn, Cottser: Convert system's system_config_form() to SystemConfigFormBase.