Add an iOS-specific version of the card unmask storage tooltip.

Add an iOS-specific version of the card unmask storage tooltip.

The existing string refers to a checkbox but the iOS ui uses a switch
component that doesn't look like a checkbox. The CL to actually use this
string is still under development but I'd like to get this in the
translation queue.

BUG=484806
Committed: https://crrev.com/7d9390443d5da1f4a38f4f61f3d901421d4c7937
Cr-Commit-Position: refs/heads/master@{#339764}

[Justin Donnelly, 2015-07-17 21:55:18]

jdonnelly@chromium.org changed reviewers:
+ stuartmorgan@chromium.org

[stuartmorgan, 2015-07-20 22:06:41]

lgtm

[Justin Donnelly, 2015-07-21 20:51:51]

The CQ bit was checked by jdonnelly@chromium.org

[Justin Donnelly, 2015-07-21 20:51:52]

The CQ bit was unchecked by jdonnelly@chromium.org

[Justin Donnelly, 2015-07-21 20:52:12]

The CQ bit was checked by jdonnelly@chromium.org

[commit-bot: I haz the power, 2015-07-21 20:53:15]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1233313010/1

[commit-bot: I haz the power, 2015-07-21 22:27:20]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-21 22:29:31]

Patchset 1 (id:??) landed as
https://crrev.com/7d9390443d5da1f4a38f4f61f3d901421d4c7937
Cr-Commit-Position: refs/heads/master@{#339764}