Scan ZIP files for local file headers, with small probability

Since every file in a ZIP must have a valid Local File Header, we can
bound the number of files in a ZIP by the number of Local File Headers.
This should exactly match the number of files extracted by ZipReader,
unless something fishy is going on.

Bug: 873766
Change-Id: Idba1788ebd3dada29a9e847569f0af692e097c8c
Reviewed-on: https://chromium-review.googlesource.com/c/1404056
Commit-Queue: Daniel Rubery <drubery@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Varun Khaneja <vakh@chromium.org>
Reviewed-by: Nathan Parker <nparker@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622068}
5 files changed