safe_browsing: Simplify code in ReadData() by calling base::MD5String().

safe_browsing: Simplify code in ReadData() by calling base::MD5String().

base's MD5String() is a helper function that does exactly what this
piece of code in ReadData() is doing, so we can just call MD5String()
and simplify it instead.

BUG=None
R=mattm@chromium.org

Committed: https://crrev.com/bd58f1007a35d83ca8e5441d744795b7c14410e6
Cr-Commit-Position: refs/heads/master@{#323998}

[tfarina, 2015-04-06 22:57:43]

PTAL

[mattm, 2015-04-07 00:57:37]

The CQ bit was checked by mattm@chromium.org

[mattm, 2015-04-07 00:57:38]

lgtm

[commit-bot: I haz the power, 2015-04-07 00:57:58]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1054433004/1

[commit-bot: I haz the power, 2015-04-07 01:23:45]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-07 01:24:29]

Patchset 1 (id:??) landed as
https://crrev.com/bd58f1007a35d83ca8e5441d744795b7c14410e6
Cr-Commit-Position: refs/heads/master@{#323998}