Changes in 20210124091450

Built from e65982f456435928e5ed52db9a96d12836663e7a

..index..
Bug 1572798 R[Core:DOM: Core & HTML]Video element created using document.open() doesn't work
Bug 1687820 R[Core:DOM: Forms]Null bytes in form payloads
Bug 1688352 R[Core:JavaScript Engine]Allocate vector/map variant of SharedDataContainer on heap
Bug 1688327 N[Core:JavaScript Engine]Simplify JS class-field-initializer parsing
Bug 1686249 R[Core:JavaScript: GC]Replace the GC mode with two GC parameters
Bug 1682919 R[Core:Panning and Zooming]Top and bottom of the page flicker when scroll with scroll up/down button
Bug 1687868 R[Core:Widget]many fuzzy reftest failures when enabling the non-native theme
Bug 1583901 A[DevTools:Inspector: Rules][Inactive CSS] Display a warning when 'fill-*', 'stroke-*', or 'paint-order' are used on invalid elements
Bug 1683860 R[Firefox:Search]Default search engine telemetry is not updated if the engine is modified
Bug 1688372 R[Firefox Build System:Source Code Analysis]error: reference to ‘Glyph’ is ambiguous
Bug 1686002 R[GeckoView:General]Bing image search locks up GeckoView
Bug 1687375 R[Toolkit:Add-ons Manager]UX: Badge descriptions may give undesired impression
Bug 1679688 R[WebExtensions:Untriaged]host permissions or <all_urls> permission should grant access to privileged parts of the tabs API
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Changes to 13 bugs - 11 fixed.