[Extensions Toolbar Mac] Adjust button threshold for hiding

[Extensions Toolbar Mac] Adjust button threshold for hiding

Since the toolbar frame now includes the proper padding,
icons are a little too eager to show after adjusting the
chevron.  Make them a bit more shy again (hide them if they
have >= 3px not displayed when adjusting the toolbar).

BUG=452475
Committed: https://crrev.com/6fd65634b5cff0510336bd958e85234bdd3eaf57
Cr-Commit-Position: refs/heads/master@{#313730}

[Devlin, 2015-01-29 00:42:33]

Patchset #1 (id:1) has been deleted

[Devlin, 2015-01-29 01:11:00]

rdevlin.cronin@chromium.org changed reviewers:
+ avi@chromium.org

[Devlin, 2015-01-29 01:11:01]

Please take a look when you can. :)

[Avi (use Gerrit), 2015-01-29 02:52:11]

lgtm

I appreciate the polishing.

[Devlin, 2015-01-29 17:10:00]

The CQ bit was checked by rdevlin.cronin@chromium.org

[commit-bot: I haz the power, 2015-01-29 17:11:03]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/881573004/20001

[commit-bot: I haz the power, 2015-01-29 17:45:15]

Committed patchset #1 (id:20001)

[commit-bot: I haz the power, 2015-01-29 17:46:15]

Patchset 1 (id:??) landed as
https://crrev.com/6fd65634b5cff0510336bd958e85234bdd3eaf57
Cr-Commit-Position: refs/heads/master@{#313730}