Downloads: After 100 numerically deduplicated files, try timestamp

After deduplicating 100 filenames,
i.e. foo.jpg, foo (1).jpg, ... foo (100).jpg, Chrome will stop trying.

On Desktop this is acceptable, as the user gets a prompt to choose
a filename.

On Android, this is really bad, because there is no prompt to choose
an alternate filename, and the download just silently fails.

This CL starts using a timestamp after 100, and creates filenames in
the ISO 8601 format, like: foo - 2018-10-11T21:55:47.392Z.jpg

Bug: 135428
Change-Id: I13748110171f799f58c8ddf27f22eebc97149c09
Reviewed-on: https://chromium-review.googlesource.com/c/1278137
Reviewed-by: Min Qin <qinmin@chromium.org>
Commit-Queue: Tommy Li <tommycli@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599802}
2 files changed