Drive-by-fix:
- improve PreparseData::Print

Bug: chromium:923705
Change-Id: I0b0b9baf1c2cc68dccd987007081e0d5c0969c4a
Reviewed-on: https://chromium-review.googlesource.com/c/1425201
Commit-Queue: Camillo Bruni <cbruni@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Cr-Commit-Position: refs/heads/master@{#58973}