Currently, GitChange.AllFiles returns a list of byte[]. This is
inconsistent with py2 and may cause issues when byte[] is used when
string is expected.

Change-Id: I3e73bc5f71aa787f55357b8139cdeeabee056047
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2946934
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Auto-Submit: Josip Sokcevic <sokcevic@google.com>
Reviewed-by: Edward Lesmes <ehmaldonado@chromium.org>