Issue #2208609 by sun, Jalandhar, damiankloip: Move Json utility class into Drupal\Component\Serialization.

Issue #214760 follow-up by sun,  lokapujya: Revised tests for theme name in block admin shows HTML entities: excessive check_plain().

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

Issue #2236207 by znerol: Use router request context instead of request service in system breadcrumb builder.

Issue #2199845 by kay_v | scor: Merge all assertFormatterRdfa() unit test calls into one single unit test.

Issue #2239181 by sun, znerol: SessionManager::isStarted() returns TRUE even after session_write_close() has been called.

Issue #1425622 by visabhishek, dealancer: Increase length of 'type' field in search_dataset, search_index tables from 16 to 64.

Issue #2234611 by visabhishek, cs_shadow, joachim: Fix up docs for WebTestBase::drupalCreateRole method

Issue #2233787 by alexpott, xjm | tim.plunkett: Move default configuration into extension/config/install to clarify its purpose.

Issue #2241655 by tim.plunkett: EntityStorageInterface::create() should always create a "new" entity.

Issue #2238659 by Jalandhar, Gábor Hojtsy, chx: Clean up some docs in String storage classes and interfaces

Issue #2221695 by brantwynn, ianthomas_uk, grom358, ParisLiakos, Jalandhar: Remove uses of deprecated URL functions.

Issue #2232425 by danblack: Database Schema field/column default value is not properly quoted via PDO::quote().

Issue #2017475 by rodrigoaguilera, Outi, balagan: Multilingual tour for interface translation section.

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

Issue #2174021 by Xano, dawehner, damiankloip: Make \Drupal\views\Plugin\views\HandlerBase unit-testable.