Python List Comprehension does not need join() (alias of os.path.join).

Change-Id: I9d5a8610d88c35fd4e3cb101bc10b25c3d1dd7cf
Reviewed-on: https://chromium-review.googlesource.com/538453Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Loo Rong Jie <loorongjie@gmail.com>
Cr-Commit-Position: refs/heads/master@{#46027}