Issue #2571695 by dawehner, plach, stefan.r, jaredsmith, lauriii, YesCT, xjm, catch, alexpott, joelpittet, Ryan Weal, Sutharsan, subhojit777, justAChris, nlisgo, effulgentsia, rpayanm, larowlan, chx, geertvd: Remove !placeholder and unsafe string return from SafeMarkup::format()

Issue #2490388 by hussainweb, Ankit Agrawal, joelpittet, dawehner: InfoParserUnitTest web test classes mislabeled as unit tests

Issue #2551335 by alexpott, Wim Leers: Remove unnecessary SafeMarkup usage in tests and clear the static cache before every run

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

Issue #2392293 by bircher, tim.plunkett, alexpott, cilefen, gobinathm: Refactor hook_system_info_alter implementations to use ModuleUninstallValidatorInterface

Issue #2465887 by dawehner, amateescu, tim.plunkett: Extract the install/uninstall functionality to a ThemeInstaller

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

Issue #356399 by dawehner, beejeebus, catch, sidharrell, klausi, nlisgo, Josh Waihi, Berdir, martin107: Optimize the route rebuilding process to rebuild on write

git commit -m 'Issue #2377397 by Wim Leers, alexpott: Themes should use libraries, not individual stylesheets'

Issue #2324055 by dawehner, cilefen, znerol: Split up the module manager into runtime information and extension information

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 #2028053 by vegantriathlete, franxo, InternetDevels, thamas, rootwork, LewisNyman: Add typographic styles, components, and utility classes.

Issue #2337379 by skippednote, BarisW, derjochenmeyer, herom, ChandeepKhosa, kiliweb, sqndr, Palashvijay4 | LewisNyman: Rename 'branding' to 'content-header'.

Issue #2213583 by lauriii, sqndr, Crisz, herom, jamesquinton, esod, Rajendar Reddy, zserno, er.pushpinderrana, cs_shadow, amitgoyal | JayeshSolanki: Fixed Misaligned Icons in Drupal 8.x.

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

Issue #2271251 by ParisLiakos, undertext, JeroenT, StevenPatz, tim.plunkett: Remove usages of watchdog() from non-form and non-controllers.

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

Issue #2033211 by jwilson3, LewisNyman, sqndr, tim.plunkett, JamesLefrère | yannickoo: Move Seven CSS files into css directory.

Revert "Issue #2033211 by LewisNyman, tim.plunkett, JamesLefrère | yannickoo: Move Seven CSS files into css directory."

This reverts commit 16e60c42.

Issue #2033211 by LewisNyman, tim.plunkett, JamesLefrère | yannickoo: Move Seven CSS files into css directory.

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

Issue #2017257 by jason.bell, dead_arm, alexrayu, philipz, idebr, rteijeiro, emma.maria, frankbaele, LewisNyman: Create generic layout classes.

Issue #1989470 by LewisNyman, aboros, philipz, mgifford, rteijeiro, dimaro, Bès, klonos, emma.maria: Dropbutton style update for Seven.

Issue #1067408 by alexpott, Jalandhar, jessebeach, Désiré, neetu morwani, dawehner, sun: Themes do not have an installation status.

Issue #2231419 by sun, jibran, Rajendar Reddy, Jalandhar, damiankloip: Merge obsolete CachedModuleHandler into ModuleHandler.

Issue #1921044 by pakmanlh, Manuel Garcia, rteijeiro, dasjo, aboros, sqndr, LewisNyman: Align the styling of tool tips to be more consistent with Seven.

Issue #2228921 by sun: Consolidate system.module + system.theme + system.theme.disabled into core.extension config.