Update CreateMintTokenFlow() to return unique_ptr instead of raw pointer

Bug: 916176
Change-Id: I94d2adda5657b3c6a1293584bb3446375b68638e
Reviewed-on: https://chromium-review.googlesource.com/c/1459063
Reviewed-by: Clark DuVall <cduvall@chromium.org>
Reviewed-by: David Roger <droger@chromium.org>
Commit-Queue: Ayu Ishii <ayui@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631311}
3 files changed