Issue #2497667 by almaudoh, Wim Leers, Cottser, Fabianx, jaxxed: Add libraries-extend to themes' *.info.yml

Issue #2451411 by almaudoh, Shamsher_Alam, lauriii, borisson_, cilefen, davidhernandez, Cottser, Wim Leers, joelpittet: Add libraries-override to themes' *.info.yml

Issue #977844 by Wim Leers: Remove the 'every_page' option for CSS/JS assets: it is confusing, even damaging

Issue #2550467 and #2120113 by alexpott, manningpete, akalata, nlisgo, nod_, harjotsingh: Remove #value_prefix and #value_suffix from HtmlTag

Issue #2533822 by alexpott: Duplicate array keys in CssOptimizerUnitTest resulting in missing test coverage

Issue #1392754 by tss, justAChris, jhodgdon: Comply with new documentation standards for @file for namespaced class files

Issue #2491155 by mikeburrelljr, Mac_Weber, opdavies: Update drupal.org and kernel.org URLs in core modules (Follow-up to 2489912)

Issue #1833356 by grendzy: CSS files encoded in UTF-8 with BOM break the design when enabling CSS aggregation

Issue #2448691 by joshi.rohit100, rpayanm, ameymudras, lakshminp: comment at top of comment_hacks.css references removed function

Issue #2400287 by hass, cutesquirrel, borisson_, rteijeiro, pfrenssen, cilefen: Remove all occurences of sourceMappingURL and sourceURL when JS files are aggregated

Issue #2463419 by Mile23, rpayanm, hussainweb: Clean-up Test members in core/tests - ensure property definition and use of camelCase naming convention

Issue #2368797 by Wim Leers, dawehner, rteijeiro: Optimize ajaxPageState to keep Drupal 8 sites fast on high-latency networks, prevent CSS/JS aggregation from taking down sites and use HTTP GET for AJAX requests

Issue #2358981 by tadityar, tstoeckler, larowlan, mpdonadio, Devin Carlson: Provide a mechanism for dynamic library declarations

Issue #2375673 by DickJohnson, LewisNyman, lauriii, emma.maria, sqndr, Wim Leers, stephr: Split Bartik's CSS into SMACSS style components

Issue #2378263 by Wim Leers: hook_library_alter() must be manually invoked by users of LibraryDiscovery, and has no test coverage

Issue #2328919 by Mile23, YesCT, tim.plunkett: Remove () from a bunch of @covers definitions in PHPUnit

Issue #2328111 by dawehner, martin107, neclimdul: Replace most instances of the DRUPAL_ROOT constant with the app.root container parameter.

Issue #1419298 by ryanissamson, zaporylie, ohthehugemanatee, ramlev, droplet, Albert Volkman, NROTC_Webmaster, pmitchell, pillarsdotnet: Remove all trailing whitespace from Drupal core files.

Issue #2340123 by Wim Leers: Setting cache tags can be tricky: use strings instead of nested arrays to improve DX.

Issue #2142441 by Garrett Albright: Fixed [Followup needed] CSS aggregator prepends data: URLs with paths.

Issue #2270323 by sun, dawehner, neclimdul: Remove DRUPAL_ROOT constant redefinitions from unit tests.

Issue #2307717 by Wim Leers, micbar: Fixed Inform Drupal in *.libraries.yml via a new per-JS file "minified" flag whether a JS file has been minified.

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

Issue #2081153 by YesCT, lauriii, rdatar, miraj9093, Enxebre, smiro, alexpott: Remove unused local variables from core/tests.