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 #2508884 by EclipseGc, tim.plunkett, dsnopek, japerry, sravya_12, swathin, Wim Leers, Fabianx, dawehner, yched: Make contexts immutable

Issue #2377757 by EclipseGc, tim.plunkett, Frando, Berdir, japerry, dsnopek, Wim Leers, Bojhan: Expose Block Context mapping in the UI

Issue #2354889 by larowlan, dawehner, lauriii, Berdir, catch, martin107, pfrenssen, EclipseGc, Fabianx, Wim Leers, dsnopek, jibran, tim.plunkett, andypost: Make block context faster by removing onBlock event and replace it with loading from a ContextManager