Allow to create read only testing volumes.

Allow to create read only testing volumes.

TEST=Not used yet, but used in an upcoming CL.
BUG=440674
Committed: https://crrev.com/c92662526e8457e4e725ecbe1df29f475e917bab
Cr-Commit-Position: refs/heads/master@{#320877}

[mtomasz, 2015-03-17 06:37:40]

mtomasz@chromium.org changed reviewers:
+ hirono@chromium.org

[mtomasz, 2015-03-17 06:37:48]

@hirono: PTAL. Thanks.

[hirono, 2015-03-17 06:49:45]

lgtm!

[mtomasz, 2015-03-17 06:50:29]

Thanks!

[mtomasz, 2015-03-17 06:50:33]

The CQ bit was checked by mtomasz@chromium.org

[commit-bot: I haz the power, 2015-03-17 06:50:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1013973004/1

[commit-bot: I haz the power, 2015-03-17 07:03:39]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-17 07:04:04]

Patchset 1 (id:??) landed as
https://crrev.com/c92662526e8457e4e725ecbe1df29f475e917bab
Cr-Commit-Position: refs/heads/master@{#320877}