Backed out for causing bustage in TimeStamp_posix

Backout link: https://hg.mozilla.org/integration/autoland/rev/8c8bbc19e7f90f621bc92f805db1fddcdad605b4

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Crunnable&revision=092f0ef9b7cf1dc0af4a92a8712be4be761e1bbc&selectedTaskRun=a14KEpnvTpiJKDw0J4VX2A.0

Failure log: https://treeherder.mozilla.org/logviewer?job_id=324487321&repo=autoland&lineNumber=5804

"INFO - /builds/worker/fetches/sccache/sccache /builds/worker/fetches/clang/bin/clang -isysroot /builds/worker/checkouts/gecko/MacOSX10.12.sdk -std=gnu99 --target=x86_64-apple-darwin -o cmsrecinfo.o -c -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-strong -DNDEBUG -DTRIMMED=1 -DNSS_FIPS_DISABLED -DNSS_NO_INIT_SUPPORT -DNSS_X86_OR_X64 -DNSS_X64 -DNSS_USE_64 -DUSE_UTIL_DIRECTLY -DNO_NSPR_10_SUPPORT -DSSL_DISABLE_DEPRECATED_CIPHER_SUITE_NAMES -DHAVE_BSD_FLOCK -DHAVE_STRERROR -DXP_UNIX -D_REENTRANT -DDARWIN -DNSS_DISABLE_DBM -DNSS_ENABLE_DRAFT_HPKE -DNSS_DISABLE_LIBPKIX -I/builds/worker/checkouts/gecko/security/nss/lib/smime -I/builds/worker/workspace/obj-build/security/nss/lib/smime/smime_smime -I/builds/worker/workspace/obj-build/dist/include/nspr -I/builds/worker/workspace/obj-build/dist/include/private/nss -I/builds/worker/workspace/obj-build/dist/include/nss -I/builds/worker/workspace/obj-build/dist/include -fPIC -include /builds/worker/workspace/obj-build/mozilla-config.h -DMOZILLA_CLIENT -Qunused-arguments -fcrash-diagnostics-dir=/builds/worker/artifacts -fno-strict-aliasing -ffunction-sections -fdata-sections -fno-math-errno -pthread -pipe -g -Xclang -load -Xclang /builds/worker/workspace/obj-build/build/clang-plugin/libclang-plugin.so -Xclang -add-plugin -Xclang moz-check -O3 -fno-omit-frame-pointer -funwind-tables -Qunused-arguments -Wall -Wbitfield-enum-conversion -Wempty-body -Wignored-qualifiers -Wpointer-arith -Wshadow-field-in-constructor-modified -Wsign-compare -Wtype-limits -Wunreachable-code -Wunreachable-code-return -Wclass-varargs -Wfloat-overflow-conversion -Wfloat-zero-conversion -Wloop-analysis -Werror=non-literal-null-conversion -Wstring-conversion -Wtautological-overlap-compare -Wtautological-unsigned-enum-zero-compare -Wtautological-unsigned-zero-compare -Wno-error=tautological-type-limit-compare -Wno-error=deprecated-declarations -Wno-error=array-bounds -Wno-error=backend-plugin -Wno-error=return-std-move -Wno-error=atomic-alignment -Wno-error=deprecated-copy -Wformat -Wformat-security -Wno-gnu-zero-variadic-macro-arguments -Werror=implicit-function-declaration -Wno-psabi -MD -MP -MF .deps/cmsrecinfo.o.pp /builds/worker/checkouts/gecko/security/nss/lib/smime/cmsrecinfo.c
[task 2020-12-14T20:58:01.799Z] 20:58:01 INFO - make[4]: Leaving directory '/builds/worker/workspace/obj-build/security/nss/lib/smime/smime_smime'
[task 2020-12-14T20:58:01.808Z] 20:58:01 INFO - make[4]: Entering directory '/builds/worker/workspace/obj-build/mozglue/misc'
[task 2020-12-14T20:58:01.810Z] 20:58:01 INFO - /builds/worker/fetches/sccache/sccache /builds/worker/fetches/clang/bin/clang++ -isysroot /builds/worker/checkouts/gecko/MacOSX10.12.sdk -std=gnu++17 --target=x86_64-apple-darwin -o TimeStamp_posix.o -c -fvisibility=hidden -fvisibility-inlines-hidden -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-strong -DNDEBUG=1 -DTRIMMED=1 '-DMOZ_APP_BASENAME="Firefox"' '-DMOZ_APP_VENDOR="Mozilla"' -DIMPL_MFBT -DMOZ_HAS_MOZGLUE -I/builds/worker/checkouts/gecko/mozglue/misc -I/builds/worker/workspace/obj-build/mozglue/misc -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 -fPIC -DMOZILLA_CLIENT -include /builds/worker/workspace/obj-build/mozilla-config.h -Qunused-arguments -Qunused-arguments -Wall -Wbitfield-enum-conversion -Wempty-body -Wignored-qualifiers -Woverloaded-virtual -Wpointer-arith -Wshadow-field-in-constructor-modified -Wsign-compare -Wtype-limits -Wunreachable-code -Wunreachable-code-return -Wwrite-strings -Wno-invalid-offsetof -Wclass-varargs -Wempty-init-stmt -Wfloat-overflow-conversion -Wfloat-zero-conversion -Wloop-analysis -Wc++2a-compat -Wcomma -Wimplicit-fallthrough -Wunused-function -Wunused-variable -Werror=non-literal-null-conversion -Wstring-conversion -Wtautological-overlap-compare -Wtautological-unsigned-enum-zero-compare -Wtautological-unsigned-zero-compare -Wno-error=tautological-type-limit-compare -Wno-inline-new-delete -Wno-error=deprecated-declarations -Wno-error=array-bounds -Wno-error=backend-plugin -Wno-error=return-std-move -Wno-error=atomic-alignment -Wno-error=deprecated-copy -Wformat -Wformat-security -Wno-gnu-zero-variadic-macro-arguments -Wno-psabi -Wno-unknown-warning-option -fno-sized-deallocation -fno-aligned-new -fcrash-diagnostics-dir=/builds/worker/artifacts -fno-exceptions -fno-strict-aliasing -stdlib=libc++ -fno-rtti -ffunction-sections -fdata-sections -fno-exceptions -fno-math-errno -pthread -pipe -g -Xclang -load -Xclang /builds/worker/workspace/obj-build/build/clang-plugin/libclang-plugin.so -Xclang -add-plugin -Xclang moz-check -O3 -fno-omit-frame-pointer -funwind-tables -Werror -MD -MP -MF .deps/TimeStamp_posix.o.pp /builds/worker/checkouts/gecko/mozglue/misc/TimeStamp_posix.cpp
[task 2020-12-14T20:58:01.811Z] 20:58:01 ERROR - /builds/worker/checkouts/gecko/mozglue/misc/TimeStamp_posix.cpp:58:23: error: unused variable 'kNsPerUs' [-Werror,-Wunused-const-variable]
[task 2020-12-14T20:58:01.811Z] 20:58:01 INFO - static const uint16_t kNsPerUs = 1000;
[task 2020-12-14T20:58:01.811Z] 20:58:01 INFO - ^
[task 2020-12-14T20:58:01.811Z] 20:58:01 INFO - 1 error generated.
[task 2020-12-14T20:58:01.812Z] 20:58:01 ERROR - make[4]: *** [/builds/worker/checkouts/gecko/config/rules.mk:674: TimeStamp_posix.o] Error 1
[task 2020-12-14T20:58:01.812Z] 20:58:01 INFO - make[4]: Leaving directory '/builds/worker/workspace/obj-build/mozglue/misc'
[task 2020-12-14T20:58:01.812Z] 20:58:01 ERROR - make[3]: *** [/builds/worker/checkouts/gecko/config/recurse.mk:72: mozglue/misc/target-objects] Error 2
[task 2020-12-14T20:58:01.812Z] 20:58:01 INFO - make[3]: *** Waiting for unfinished jobs....
[task 2020-12-14T20:58:01.821Z] 20:58:01 INFO - make[4]: Entering directory '/builds/worker/workspace/obj-build/security/nss/lib/ssl/ssl_ssl'
[task 2020-12-14T20:58:01.821Z] 20:58:01 INFO - security/nss/lib/ssl/ssl3con.o
[task 2020-12-14T20:58:01.824Z] 20:58:01 INFO - /builds/worker/fetches/sccache/sccache /builds/worker/fetches/clang/bin/clang -isysroot /builds/worker/checkouts/gecko/MacOSX10.12.sdk -std=gnu99 --target=x86_64-apple-darwin -o ssl3con.o -c -U_FORTIFY_SOURCE -D_FORTIFY_SOURCE=2 -fstack-protector-strong -DNDEBUG -DTRIMMED=1 -DNSS_FIPS_DISABLED -DNSS_NO_INIT_SUPPORT -DNSS_X86_OR_X64 -DNSS_X64 -DNSS_USE_64 -DNSS_ALLOW_SSLKEYLOGFILE -DUSE_UTIL_DIRECTLY -DNO_NSPR_10_SUPPORT -DSSL_DISABLE_DEPRECATED_CIPHER_SUITE_NAMES -DHAVE_BSD_FLOCK -DHAVE_STRERROR -DXP_UNIX -D_REENTRANT -DDARWIN -DNSS_DISABLE_DBM -DNSS_ENABLE_DRAFT_HPKE -DNSS_DISABLE_LIBPKIX -I/builds/worker/checkouts/gecko/security/nss/lib/ssl -I/builds/worker/workspace/obj-build/security/nss/lib/ssl/ssl_ssl -I/builds/worker/workspace/obj-build/dist/include/nspr -I/builds/worker/workspace/obj-build/dist/include/private/nss -I/builds/worker/workspace/obj-build/dist/include/nss -I/builds/worker/workspace/obj-build/dist/include -fPIC -include /builds/worker/workspace/obj-build/mozilla-config.h -DMOZILLA_CLIENT -Qunused-arguments -fcrash-diagnostics-dir=/builds/worker/artifacts -fno-strict-aliasing -ffunction-sections -fdata-sections -fno-math-errno -pthread -pipe -g -Xclang -load -Xclang /builds/worker/workspace/obj-build/build/clang-plugin/libclang-plugin.so -Xclang -add-plugin -Xclang moz-check -O3 -fno-omit-frame-pointer -funwind-tables -Qunused-arguments -Wall -Wbitfield-enum-conversion -Wempty-body -Wignored-qualifiers -Wpointer-arith -Wshadow-field-in-constructor-modified -Wsign-compare -Wtype-limits -Wunreachable-code -Wunreachable-code-return -Wclass-varargs -Wfloat-overflow-conversion -Wfloat-zero-conversion -Wloop-analysis -Werror=non-literal-null-conversion -Wstring-conversion -Wtautological-overlap-compare -Wtautological-unsigned-enum-zero-compare -Wtautological-unsigned-zero-compare -Wno-error=tautological-type-limit-compare -Wno-error=deprecated-declarations -Wno-error=array-bounds -Wno-error=backend-plugin -Wno-error=return-std-move -Wno-error=atomic-alignment -Wno-error=deprecated-copy -Wformat -Wformat-security -Wno-gnu-zero-variadic-macro-arguments -Werror=implicit-function-declaration -Wno-psabi -MD -MP -MF .deps/ssl3con.o.pp /builds/worker/checkouts/gecko/security/nss/lib/ssl/ssl3con.c
[task 2020-12-14T20:58:01.824Z] 20:58:01 INFO - make[4]: Leaving directory '/builds/worker/workspace/obj-build/security/nss/lib/ssl/ssl_ssl'"

Now is already supported when CLOCK_MONOTONIC is supported, but
ComputeProcessUptime is not. This shares the code with other BSDs, and
makes it look like the implementation in Timestamp_darwin.cpp.

Eventually, we'll remove the one from Timestamp_darwin.cpp.

https://hg.mozilla.org/mozilla-central/rev/38d0eb18ea7a
https://hg.mozilla.org/mozilla-central/rev/3246c882a0da

Backed out for causing Bug 1684265

Backout link: https://hg.mozilla.org/integration/autoland/rev/2b0a7c54779c0cc074f6b5225a8d343d01803f21

Backout merged: https://hg.mozilla.org/mozilla-central/rev/2b0a7c54779c