Changes in 20210621094223

Built from 2ad6d795630df04703a887f12f2fdba219bf7f4f

..index..
Bug 1716728 R[Core:DOM: Editor]Remove mPaddingBRElementForEmptyEditor use from TextEditor
Bug 1715300 R[Core:DOM: Navigation]Enable BFCache in parent when Fission is enabled
Bug 1677253 R[Core:DOM: Selection]Fix <input>/<textarea> selection setters/methods always firing a select event regardless of its current selection range
Bug 1716925 R[Core:Graphics: WebRender]Remove use of DefineClip in ClipManager
Bug 1716933 R[Core:Graphics: WebRender]Remove DefineClip API from WR public API
Bug 1716044 R[Core:Graphics: WebRender]Fix WebGL in combination with compositor integration
Bug 1716006 R[Core:Graphics: WebRender]Crash in [@ mozilla::detail::MutexImpl::lock | mozilla::layers::NativeSurfaceWayland::FrameCallbackHandler]
Bug 1686951 R[Firefox:Address Bar]Support switch-to-tab in Private Browsing windows
Bug 1265208 R[Firefox:Address Bar]URL cut from address bar is not restored when switching between tabs.
Bug 1673511 R[GeckoView:General][Bug] weird sticky keyboard pop up behaviour
Bug 1690417 R[Toolkit:Reader Mode]Tooltip appears under Reader mode menu
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Changes to 11 bugs - 10 fixed.