Changes in 20210117095130

Built from 1c14bc8527e7dee848e867d86a614ceedc396cb0

..index..
Bug 1686947 R[Core:DOM: Content Processes]Fix code links to jsactor documentation
Bug 1687052 R[Core:DOM: UI Events & Focus Handling]Remove some test_wpt_test_* which are no longer manual test in wpt and we could pass the wpt one
Bug 1686827 R[Core:Disability Access APIs]GeckoTextMarker lesser than operator returns wrong result when comparing a point in a link and a point at its start offset
Bug 1686848 R[Core:Graphics: WebRender]Add fallback handling of FLIP_SEQUENTIAL init failure
Bug 1667804 R[Core:JavaScript Engine]Enable stencil-mvp by default
Bug 1666009 R[Core:JavaScript Engine: JIT]Increase maximum bytecode size when trial inlining self-hosted functions
Bug 1686787 R[Core:JavaScript: GC]Win32 debug SM(cgc) task fails at pretenuring.js:32:9 with clang 12
Bug 1551040 R[Core:Layout]Make prefers-color-scheme affect plain text documents
Bug 1686326 R[Core:Layout: Block and Inline][quirks] Chrome allows negative top margin on <button> to position them in transitional DTD, Firefox does not.
Bug 1681788 V[Core:Layout: Flexbox]Assertion failure: childReflowStatus.IsComplete() (We gave flex item unconstrained available block-size, so it should be complete), at /builds/worker/checkouts/gecko/layout/generic/nsFlexContainerFrame.cpp:1924
Bug 1686220 R[Core:Layout: Generated Content, Lists, and Counters]5.96 - 27.08% wikipedia / wikipedia LastVisualChange / wikipedia fcp / wikipedia loadtime (linux64-shippable, linux64-shippable-qr, macosx1014-64-shippable-qr) regression on push facbcc4306d1a824cb607cb3bbc54a7b13d1038c (Fri January 8 2021)
Bug 1687131 R[Core:SVG]test_pointer-events-5.xhtml is a copy of test_pointer-events-2.xhtml
Bug 1683054 R[Core:Security: Process Sandboxing]RLBox template specialization regression
Bug 1588904 A[Core:Widget: Gtk][Linux/EGL] Use correct rendering device in multi-GPU setup
Bug 1687038 R[Firefox:General]Skeleton UI sometimes appears in headless mode
Bug 1683991 R[Firefox:Search]Built-in eBay search engine just sends people to ebay.com when there are multiple words in a search query
Bug 1553230 R[Firefox Build System:General]Teach moz.configure to auto-update certain tools and toolchains (e.g. clang and cbindgen)
Bug 1686967 R[Firefox Build System:General]Perma [tier2] Exception: Process executed with non-0 exit code 1: ['c:\\mozilla-build\\python3\\python3.exe', 'z:/build/build/src\\configure.py'] Return code: 1
Bug 1617369 N[Firefox Build System:Lint and Formatting][rust] Reformat the tree using rustfmt
Bug 1649611 A[Toolkit:OS.File]DownloadIntegration.jsm imports OS.File during startup
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Changes to 20 bugs - 16 fixed.