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If the data parameter is undefined the API will clear the current stored
data and delete the file used to store as well as its immediate folder
if it has become empty.

BUG=1044673
TEST=unit_tests

Change-Id: I2f4dd796c9b0e4eea2474def32a47924d0195ccc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2015168Reviewed-by: Owen Min <zmin@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Commit-Queue: Julian Pastarmov <pastarmovj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735346}