It's been enabled by default for about 3 years now (bug 1720131). Let's remove this feature rollout pref

• dom/webidl/FontFace.webidl#22,27
• layout/style/FontFaceImpl.cpp#492
• servo/components/style/font_face.rs#579-581
• modules/libpref/init/StaticPrefList.yaml#9869-9874

Revert for causing mass build bustages related to layout_css_size_adjust_enabled.

• Push with failures

• Failure log

• Backout link

[task 2025-07-26T10:58:48.347+00:00] 10:58:48     INFO -  gmake[4]: Entering directory '/builds/worker/workspace/obj-build/dom/bindings'
[task 2025-07-26T10:58:48.352+00:00] 10:58:48     INFO -  /builds/worker/fetches/sccache/sccache /builds/worker/fetches/clang/bin/clang++ --sysroot /builds/worker/fetches/sysroot-i686-linux-gnu -m32 -o WebIDLPrefs.o -c  -I/builds/worker/workspace/obj-build/dist/stl_wrappers -I/builds/worker/workspace/obj-build/dist/system_wrappers -include /builds/worker/checkouts/gecko/config/gcc_hidden.h -fstrict-flex-arrays=1 -D_FORTIFY_SOURCE=0 -fno-common -DNDEBUG=1 -DTRIMMED=1 -DGOOGLE_PROTOBUF_NO_RTTI -DGOOGLE_PROTOBUF_NO_STATIC_INITIALIZER -DMOZ_HAS_MOZGLUE -DMOZILLA_INTERNAL_API -DIMPL_LIBXUL -DMOZ_SUPPORT_LEAKCHECKING -DSTATIC_EXPORTABLE_JS_API -I/builds/worker/checkouts/gecko/dom/bindings -I/builds/worker/workspace/obj-build/dom/bindings -I/builds/worker/workspace/obj-build/dist/include/mozilla/dom -I/builds/worker/checkouts/gecko/dom/base -I/builds/worker/checkouts/gecko/dom/battery -I/builds/worker/checkouts/gecko/dom/canvas -I/builds/worker/checkouts/gecko/dom/geolocation -I/builds/worker/checkouts/gecko/dom/html -I/builds/worker/checkouts/gecko/dom/indexedDB -I/builds/worker/checkouts/gecko/dom/media/webaudio -I/builds/worker/checkouts/gecko/dom/media/webrtc -I/builds/worker/checkouts/gecko/dom/media/webrtc/common/time_profiling -I/builds/worker/checkouts/gecko/dom/media/webrtc/jsapi -I/builds/worker/checkouts/gecko/dom/media/webrtc/libwebrtcglue -I/builds/worker/checkouts/gecko/dom/media/webrtc/transport -I/builds/worker/checkouts/gecko/dom/media/webspeech/recognition -I/builds/worker/checkouts/gecko/dom/svg -I/builds/worker/checkouts/gecko/dom/xml -I/builds/worker/checkouts/gecko/dom/xslt/base -I/builds/worker/checkouts/gecko/dom/xslt/xpath -I/builds/worker/checkouts/gecko/dom/xul -I/builds/worker/checkouts/gecko/js/xpconnect/src -I/builds/worker/checkouts/gecko/js/xpconnect/wrappers -I/builds/worker/checkouts/gecko/layout/generic -I/builds/worker/checkouts/gecko/layout/style -I/builds/worker/checkouts/gecko/layout/xul/tree -I/builds/worker/checkouts/gecko/media/webrtc -I/builds/worker/checkouts/gecko/netwerk/base -I/builds/worker/checkouts/gecko/third_party/abseil-cpp -I/builds/worker/checkouts/gecko/third_party/libwebrtc -I/builds/worker/checkouts/gecko/third_party/msgpack/include -I/builds/worker/workspace/obj-build/ipc/ipdl/_ipdlheaders -I/builds/worker/checkouts/gecko/ipc/chromium/src -I/builds/worker/workspace/obj-build/dist/include -I/builds/worker/workspace/obj-build/dist/include/nspr -I/builds/worker/workspace/obj-build/dist/include/nss -DMOZILLA_CLIENT -include /builds/worker/workspace/obj-build/mozilla-config.h -fsanitize=address -fsanitize=bool,bounds,enum,function,integer-divide-by-zero,pointer-overflow,return,vla-bound,object-size -fno-sanitize-recover=bool,bounds,enum,function,integer-divide-by-zero,pointer-overflow,return,vla-bound,object-size -fsanitize-blacklist=/builds/worker/workspace/obj-build/ubsan_blacklist.txt -fno-rtti -pthread -fno-sized-deallocation -fno-aligned-new -ffunction-sections -fdata-sections -fno-math-errno -fno-exceptions -fPIC -fcrash-diagnostics-dir=/builds/worker/artifacts -march=pentium-m -msse -msse2 -mfpmath=sse -fcrash-diagnostics-dir=/builds/worker/artifacts -gline-tables-only -Xclang -load -Xclang /builds/worker/workspace/obj-build/build/clang-plugin/libclang-plugin.so -Xclang -add-plugin -Xclang moz-check -O2 -fno-omit-frame-pointer -funwind-tables -Werror -Wall -Wbitfield-enum-conversion -Wempty-body -Wformat-type-confusion -Wignored-qualifiers -Wpointer-arith -Wshadow-field-in-constructor-modified -Wsign-compare -Wtautological-constant-in-range-compare -Wtype-limits -Wno-error=tautological-type-limit-compare -Wunreachable-code -Wunreachable-code-return -Wunused-but-set-parameter -Wno-invalid-offsetof -Wclass-varargs -Wempty-init-stmt -Wfloat-overflow-conversion -Wfloat-zero-conversion -Wloop-analysis -Wno-range-loop-analysis -Wenum-compare-conditional -Wenum-float-conversion -Wno-deprecated-anon-enum-enum-conversion -Wno-deprecated-enum-enum-conversion -Wno-deprecated-this-capture -Wcomma -Wimplicit-fallthrough -Wstring-conversion -Wno-inline-new-delete -Wno-error=deprecated-declarations -Wno-error=array-bounds -Wno-error=free-nonheap-object -Wno-error=atomic-alignment -Wno-error=deprecated-builtins -Wformat -Wformat-security -Wno-psabi -Wthread-safety -Wno-error=builtin-macro-redefined -Wno-vla-cxx-extension -Wno-unknown-warning-option -fno-strict-aliasing -ffp-contract=off  -MD -MP -MF .deps/WebIDLPrefs.o.pp   WebIDLPrefs.cpp
[task 2025-07-26T10:58:48.353+00:00] 10:58:48    ERROR -  WebIDLPrefs.cpp:218:16: error: no member named 'layout_css_size_adjust_enabled' in namespace 'mozilla::StaticPrefs'
[task 2025-07-26T10:58:48.353+00:00] 10:58:48     INFO -    218 |   StaticPrefs::layout_css_size_adjust_enabled,
[task 2025-07-26T10:58:48.354+00:00] 10:58:48     INFO -        |   ~~~~~~~~~~~~~^
[task 2025-07-26T10:58:48.355+00:00] 10:58:48     INFO -  1 error generated.
[task 2025-07-26T10:58:48.356+00:00] 10:58:48    ERROR -  gmake[4]: *** [/builds/worker/checkouts/gecko/config/rules.mk:676: WebIDLPrefs.o] Error 1
[task 2025-07-26T10:58:48.356+00:00] 10:58:48     INFO -  gmake[4]: Leaving directory '/builds/worker/workspace/obj-build/dom/bindings'
[task 2025-07-26T10:58:48.357+00:00] 10:58:48     INFO -  gmake[4]: Entering directory '/builds/worker/workspace/obj-build/dom/bindings'
[task 2025-07-26T10:58:48.358+00:00] 10:58:48     INFO -  dom/bindings/WebIDLSerializable.o
[task 2025-07-26T10:58:48.359+00:00] 10:58:48     INFO -  gmake[4]: Leaving directory '/builds/worker/workspace/obj-build/dom/bindings'

Sorry about that, it didn't get included into the patch for some reason

Thanks Daniel :)

https://hg.mozilla.org/mozilla-central/rev/1901f0e0dd78
https://hg.mozilla.org/mozilla-central/rev/1f8bd7536973