Bug 1604989 R[Core:CSS Parsing and Computation]CSS Shadow Parts rules only apply to first of type
Bug 1604296 R[Core:DOM: CSS Object Model]Create Constructable Stylesheets WebIDL API Under a Preference
Bug 1594748 R[Core:DOM: Core & HTML]Enable "resab" on Nightly (aka quadruple pref flip)
Bug 1604761 R[Core:Disability Access APIs]Firefox doesn't apply gnome "Large Text" accessibility setting to web content
Bug 1600652 R[Core:Graphics: WebRender]Floating text selection toolbar misplaced above the selection
Bug 1606379 R[Core:JavaScript Engine]Drop gdb prettyprinter test task down to tier 2
Bug 1606080 R[Core:JavaScript Engine]Rewrite and simplify generator resume/yield bytecode
Bug 1605854 N[Core:JavaScript Engine]Fix some Firefox tests that use uneval/toSource
Bug 1605591 R[Core:JavaScript Engine: JIT]Check if bytecode exists before accessing length in JITs
Bug 1499281 R[Core:Layout: Columns]Remove preference "layout.css.column-span.enabled" after it reaches the release channel
Bug 1144465 R[Core:Layout: Ruby]Text inside ruby is not bidi reordered
Bug 1606410 R[Core:XPCOM]Change how idle state peeking works to make its API more similar to idle state getting
Bug 1606472 R[DevTools:Performance Tools (Profiler/Timeline)]JSM imports are not properly typed
Bug 1606452 R[Firefox Build System:Bootstrap Configuration]Error calling ./mach clang-format: You're using an old version of clang-format binary
Bug 1606160 R[Firefox Build System:General]mozbuild/base.py and mozbuild/mozconfig.py support Python 3
Bug 1605264 R[Firefox Build System:General]"./mach package" should use Python 3
Bug 1606340 R[Firefox Build System:General]mozbuild/test/test_line_endings.py supports Python 3
Bug 1606336 R[Firefox Build System:General]mozbuild/mozinfo.py supports Python 3
Bug 1602863 N[Firefox Build System:Task Configuration]ubuntu1804 - migrate tasks, tests and other jobs that use desktop1604-test to use ubuntu1804-test image
Bug 1606501 N[Release Engineering:Applications: MozharnessCore][mozharness] make mozharness/external_tools python3 compatible
Bug 1532427 R[Release Engineering:Applications: MozharnessCore]Support python 3 in mozharness
Bug 1605275 N[Release Engineering:General]Add a tool to make testing scriptworker changes against mozilla-central easier.
Bug 1604749 R[Thunderbird:Build Config]daily cron job won't start
Bug 1605030 R[Thunderbird:Testing Infrastructure]Remove mozmill tests and infrastructure from the tree
Bug 1579581 R[Toolkit:Telemetry]Gather remaining CPU and OS info in telemetry environment off-main-thread and later on startup.
Bug 1603946 R[WebExtensions:Untriaged]Perma xpcshell.ini:browser/components/extensions/test/xpcshell/test_ext_pageAction_shutdown.js | xpcshell return code: 0 when Gecko 73 merges to Beta on 2020-01-06
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Changes to 27 bugs - 21 fixed.