[Password Manager] Offer to save when an iframe is detached

[Password Manager] Offer to save when an iframe is detached

If the user has already entered data into a form and the frame containing it
is detached, prompt to save. This fixes password saving on Sears.com, as
they perform authentication by removing an iframe containing the login information when submission is successful.

BUG=450806
Committed: https://crrev.com/92a33acc60e555d9a45cc8f6db686a4007173057
Cr-Commit-Position: refs/heads/master@{#321486}

[Garrett Casto, 2015-03-18 07:22:26]

gcasto@chromium.org changed reviewers:
+ dvadym@chromium.org, vabr@chromium.org

[Garrett Casto, 2015-03-18 07:22:26]

Not that this CL depends on https://codereview.chromium.org/1012853002/ which
still hasn't landed yet.

[vabr (Chromium), 2015-03-18 08:33:44]

LGTM!

[Garrett Casto, 2015-03-19 22:57:17]

The CQ bit was checked by gcasto@chromium.org

[commit-bot: I haz the power, 2015-03-19 22:57:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1012093005/20001

[commit-bot: I haz the power, 2015-03-20 01:25:50]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-03-20 01:26:36]

Patchset 2 (id:??) landed as
https://crrev.com/92a33acc60e555d9a45cc8f6db686a4007173057
Cr-Commit-Position: refs/heads/master@{#321486}