Use the substr API correctly in FullHashToHashPrefix.

Use the substr API correctly in FullHashToHashPrefix.

This code path is only used for permissions blacklists so the rest of
PVer4 launch can progress as-is.

Bug: 729809
Change-Id: Iec6af24fadae59c6e16c109c0990bc6159575e60
Reviewed-on: https://chromium-review.googlesource.com/524892
Reviewed-by: Jialiu Lin <jialiul@chromium.org>;
Reviewed-by: Nathan Parker <nparker@chromium.org>;
Commit-Queue: Varun Khaneja <vakh@chromium.org>;
Cr-Original-Commit-Position: refs/heads/master@{#477292}
Review-Url: https://codereview.chromium.org/2928793002 .
Cr-Commit-Position: refs/branch-heads/3112@{#228}
Cr-Branched-From: b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed: https://chromium.googlesource.com/chromium/src/+/203a0320bd08e0a1832c2692309783de3aa66aab

[Jialiu Lin, 2017-06-07 19:04:11]

Description was changed from

==========
Use the substr API correctly in FullHashToHashPrefix.

This code path is only used for permissions blacklists so the rest of
PVer4 launch can progress as-is.

Bug: 729809
Change-Id: Iec6af24fadae59c6e16c109c0990bc6159575e60
Reviewed-on: https://chromium-review.googlesource.com/524892
Reviewed-by: Jialiu Lin <jialiul@chromium.org>
Reviewed-by: Nathan Parker <nparker@chromium.org>
Commit-Queue: Varun Khaneja <vakh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#477292}
(cherry picked from commit 1e66b2698e1e71e9266c761f3fdac8b458c720f4)
==========

to

==========
Use the substr API correctly in FullHashToHashPrefix.

This code path is only used for permissions blacklists so the rest of
PVer4 launch can progress as-is.

Bug: 729809
Change-Id: Iec6af24fadae59c6e16c109c0990bc6159575e60
Reviewed-on: https://chromium-review.googlesource.com/524892
Reviewed-by: Jialiu Lin <jialiul@chromium.org>
Reviewed-by: Nathan Parker <nparker@chromium.org>
Commit-Queue: Varun Khaneja <vakh@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#477292}
Review-Url: https://codereview.chromium.org/2928793002 .
Cr-Commit-Position: refs/branch-heads/3112@{#228}
Cr-Branched-From:
b6460e24cf59f429d69de255538d0fc7a425ccf9-refs/heads/master@{#474897}
Committed:
https://chromium.googlesource.com/chromium/src/+/203a0320bd08e0a1832c26923097...
==========

[Jialiu Lin, 2017-06-07 19:04:13]

Committed patchset #1 (id:1) manually as
203a0320bd08e0a1832c2692309783de3aa66aab.