Make sure to call MaybeProcessSourceRanges in ParseOnBackground so that
code coverage ranges match between main thread and background compiles.

Bug: chromium:1011762
Change-Id: Ic6194083e425f4160e34a34bceb6034624cf1b9f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2120540Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66872}