[Easy Unlock] Add a histogram measuring whether authentication succeeds or fails.

[Easy Unlock] Add a histogram measuring whether authentication succeeds or fails.

The authentication is attempted when establishing a secure connection with the
remote device.

BUG=411043
TEST=none
NOTRY=true
R=jwd@chromium.org

Committed: https://crrev.com/2e214753e55b67c5373af77e0176c4708cc04474
Cr-Commit-Position: refs/heads/master@{#294880}

[jwd, 2014-09-15 18:04:57]

lgtm

[Ilya Sherman, 2014-09-15 20:11:27]

The CQ bit was checked by isherman@chromium.org

[commit-bot: I haz the power, 2014-09-15 20:12:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/566073002/1

[commit-bot: I haz the power, 2014-09-15 20:23:51]

Committed patchset #1 (id:1) as 036db77380cacc7a2feea98b397ead9be1d8023c

[commit-bot: I haz the power, 2014-09-15 20:26:26]

Patchset 1 (id:??) landed as
https://crrev.com/2e214753e55b67c5373af77e0176c4708cc04474
Cr-Commit-Position: refs/heads/master@{#294880}