Changes in 20210509080024

Built from ca56a49fd420516b7200d4d680ea83b8d118c175

..index..
Bug 1710096 R[Core:Layout: Text and Fonts]Update mapped_hyph to replace the unmaintained memmap crate with memmap2
Bug 1710211 V[Core:Layout: Text and Fonts]Permafailing /css/css-fonts/variations/variable-opsz-size-adjust.html | Testing css-fonts/variations/variable-opsz-size-adjust.html == css-fonts/variations/variable-opsz-size-adjust-ref.h when Gecko 90 merges to Beta on 2021-05-31
Bug 1710059 R[Core:Panning and Zooming][fission] Hit testing scaled remote iframes is broken.
Bug 1709719 R[Core:Widget: Gtk]Transparent context menu background on right click (Linux Gnome 40)
Bug 1710119 R[Firefox:Tabbed Browser]Selected tab and tab hover feedback lack contrast in high contrast mode
Bug 1710082 R[Firefox:Theme]--toolbarbutton-icon-fill-attention lacks contrast in High Contrast mode on Windows
Bug 1709506 R[Firefox Build System:Documentation Infrastructure]HTML link is not parsed in https://firefox-source-docs.mozilla.org/contributing/build/artifact_builds.html#things-that-are-not-supported
Bug 1710185 R[Firefox Build System:General]Perma [tier2] make[4]: *** [/builds/worker/checkouts/gecko/config/rules.mk:420: ../../../../../dist/bin/certutil] Error 1 | clang-12: error: linker command failed with exit code 1
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Changes to 8 bugs - 7 fixed.