This bug is a followup of bug 1523613:

From bug 1523613 comment 6:

This fixes the leak in ApplyUpdate. The following now shows up in the log

rstrong/moz/_1_mozilla-central/ff-lsan-leak/dist/Nightly.app/Contents/MacOS/XUL:x86_64+0xe1e2077)
1:13.91 pid:59970 Direct leak of 823 byte(s) in 5 object(s) allocated from:
1:13.91 pid:59970 #0 0x10219b28c in wrap_strdup (/usr/local/opt/llvm/lib/clang/7.0.1/lib/darwin/libclang_rt.asan_osx_dynamic.dylib:x86_64+0x5328c)
1:13.91 pid:59970 #1 0x11231791f in CommandLineServiceMac::SetupMacCommandLine(int&, char**&, bool) (/Users/rstrong/moz/_1_mozilla-central/ff-lsan-leak/dist/Nightly.app/Contents/MacOS/XUL:x86_64+0xdf5291f)
1:13.91 pid:59970 #2 0x112311872 in mozilla::detail::RunnableFunction<UpdateDriverSetupMacCommandLine(int&, char**&, bool)::$_0>::Run() (/Users/rstrong/moz/_1_mozilla-central/ff-lsan-leak/dist/Nightly.app/Contents/MacOS/XUL:x86_64+0xdf4c872)
1:13.91 pid:59970 #3 0x1046c64d9 in nsThread::ProcessNextEvent(bool, bool*) (/Users/rstrong/moz/_1_mozilla-central/ff-lsan-leak/dist/Nightly.app/Contents/MacOS/XUL:x86_64+0x3014d9)