Truncate the length of downloaded file name on windows

During annotation, an extra 16 characters(zone identifier)
are appended to the file name.
That may cause the file path to exceed the 260 character limit.
This CL fixes that problem by truncating the file name when generating
it.

BUG=809759
TBR=qinmin@chromium.org

(cherry picked from commit c575e74530267932837e074fa4cdb3df4069d497)

Change-Id: Ie0baa318ccf5824e3ed4df8cf23386653b6747d7
Reviewed-on: https://chromium-review.googlesource.com/919445
Commit-Queue: Min Qin <qinmin@chromium.org>
Reviewed-by: Eric Lawrence <elawrence@chromium.org>
Reviewed-by: David Trainor <dtrainor@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#537093}
Reviewed-on: https://chromium-review.googlesource.com/927041
Reviewed-by: Min Qin <qinmin@chromium.org>
Cr-Commit-Position: refs/branch-heads/3325@{#509}
Cr-Branched-From: bc084a8b5afa3744a74927344e304c02ae54189f-refs/heads/master@{#530369}
2 files changed