Mac: Display a native bubble (instead of the JS one) after the web signin flow. 

XIB changes: Deleted "Undo" button from the Bubble dialog, and copied the InformativePlaceholderText from  chrome/app/nibs/OneClickSigninDialog.xib, which allows the "Learn More" link to be displayed.

Part of a 3 CL Voltron, along with: 
[Win] https://codereview.chromium.org/13979003/ 
[GTK] https://codereview.chromium.org/14258007/

(branched off https://codereview.chromium.org/13979003/)

BUG=119728
TEST=Open Chrome. Delete all your profiles, so that you have a fresh one. Open a new tab, and press the "sign in" link in the top right corner. Sign in. Upon completion, this should show a native popup bubble, anchored off the wrench menu. If you try to log in with the same email in another profile, the bubble should display a sad error message. Check out the issue description for screenshots.

Review URL: https://chromiumcodereview.appspot.com/13845022

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@197769 0039d316-1c4b-4281-b951-d872f2087c98
11 files changed