[parser] Cleanup and streamline ParsePropertyName

Change-Id: I985ba650bb6623bcd399926ac2254dd7f5d3bee6
Reviewed-on: https://chromium-review.googlesource.com/1235925
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Igor Sheludko <ishell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56098}