Additionally, drive-by add a test inspired by a worrying TODO
in the parser.

Cq-Include-Trybots: master.tryserver.v8:v8_linux_noi18n_rel_ng,master.tryserver.v8:v8_linux64_msan_rel,v8_linux64_tsan_rel,v8_linux_arm64_dbg,v8_linux_gc_stress_dbg,v8_linux_noi18n_rel_ng,v8_linux_nosnap_rel

Change-Id: I693a858a638753f8c1091f2f9086710f628b40dd
Reviewed-on: https://chromium-review.googlesource.com/553677Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Daniel Ehrenberg <littledan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#46634}