The ETag's for some of the crx files contain non alpha
and non digit characters like '='.

Bug:1225491
Bug:b/191630810
Change-Id: Id43ed8ea5fc17825731dd1605c7d6358ceed39cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3287293Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Rakib Hasan <rmhasan@google.com>