Changes in 20210802093840

Built from afcdd8e3c67656f49be753e0cf04f18838639543

..index..
Bug 1722488 R[Core:CSS Parsing and Computation]Add some WPTs for system-ui
Bug 1722689 R[Core:Canvas: 2D]Canvas renders font too large
Bug 1720615 R[Core:DOM: Core & HTML]Remove or update probes expiring in Firefox 93: WINDOW_OPEN_TYPE
Bug 1677324 R[Core:DOM: Navigation][Fission] White / grey flash when navigating across origins
Bug 1722978 R[Core:DOM: Security]Update tests within docshell/ to work with https-first enabled
Bug 1652560 R[Core:Gecko Profiler]Allow emitting Gecko profiler labels and stack categories from Rust code (All Rust threads currently marked as non-idle)
Bug 1577199 R[Core:WebRTC: Audio/Video]Evaluate Feature policy allow/block "speaker-selection" in WebRTC API
Bug 1720369 R[Firefox:Private Browsing]Switch to Tab option appears in Private window for non-Private Tab Using Search Shortcut
Bug 1665476 N[Thunderbird:General]LW-theme background images aren't shown
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Changes to 9 bugs - 8 fixed.