Fix Mac password bubble crash due to the "nope" menu hanging around.

Fix Mac password bubble crash due to the "nope" menu hanging around.

By default open menus in Cocoa exist until the user makes a choice, but
since the bubble and its backing controller are owned and managed by
cross-platform code, this model doesn't make sense. Hiding the menu
programmatically matches the Views implementation and fixes the crash.

Since triggering the NSPopUpButton's menu with |performClick:| spins
a run loop waiting for user input, getting a test working was extremely
difficult. The solution is to refactor BubbleCombobox to subclass
MenuButton instead of NSPopUpButton; http://crbug.com/415088 created
to track this work, which will then support a test for this bug.

BUG=413267
Committed: https://crrev.com/0912e40030390bd3cc20b955ebc57c02dbe6fb5a
Cr-Commit-Position: refs/heads/master@{#296398}

[dconnelly, 2014-09-17 11:42:07]

Patchset #1 (id:1) has been deleted

[dconnelly, 2014-09-17 11:43:54]

dconnelly@chromium.org changed reviewers:
+ rohitrao@chromium.org

[dconnelly, 2014-09-23 16:19:19]

friendly ping

[rohitrao (ping after 24h), 2014-09-24 11:44:56]

LGTM

Sorry, for some reason I thought this was already landed.

[dconnelly, 2014-09-24 11:46:30]

The CQ bit was checked by dconnelly@chromium.org

[commit-bot: I haz the power, 2014-09-24 11:46:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/563093003/20001

[commit-bot: I haz the power, 2014-09-24 12:53:08]

Committed patchset #1 (id:20001) as df91b46e99a36c56a0c544b1baede71639581e42

[commit-bot: I haz the power, 2014-09-24 12:53:38]

Patchset 1 (id:??) landed as
https://crrev.com/0912e40030390bd3cc20b955ebc57c02dbe6fb5a
Cr-Commit-Position: refs/heads/master@{#296398}