Changes in 20200927094310

Built from 4668c7b5e842a7afef9e4c183c8a85af950eb1ad

..index..
Bug 1660661 R[Core:Canvas: 2D]2 reftest fuzz expectations need updating for running on windows 10 hardware
Bug 1667307 R[Core:Internationalization]Update fluent-rs to 0.13
Bug 1643948 R[Core:JavaScript Engine: JIT]CacheIR: Optimize arguments[Symbol.iterator]
Bug 1666853 R[Core:JavaScript: GC]Attempt to improve the code generated for GC barriers
Bug 1666880 V[Core:JavaScript: GC]Assertion failure: !marker->tracingZone, at gc/Marking.cpp:504 with TypedObject and BigInt
Bug 1658308 N[Core:JavaScript: Standard Library]Implement the .item proposal
Bug 1667594 N[Core:Layout]Reduce the recompile time of nsLayoutUtils.h
Bug 1667507 R[Core:Layout: Positioned]Relax a failure-prone layout assertion "MOZ_ASSERT(kidOverflowBEnd >= kidBEnd)" to be non-fatal
Bug 1667469 R[Core:Layout: Scrolling and Overflow]fix layout/base/tests/test_scroll_space_no_range_overflow_scroll.html
Bug 1667478 R[Core:Layout: Scrolling and Overflow]fix dom/events/test/pointerevents/test_bug1303704.html
Bug 1667118 R[Core:MathML]Rename -moz-math-script-level to math-depth
Bug 1667475 N[Core:Panning and Zooming]Some displayport-related cleanups
Bug 1656689 R[Core:Panning and Zooming]Keyboard scrolling not working while zoomed in with touchpad
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Changes to 13 bugs - 8 fixed.