[rAC, OSX] Polish for autofill bubble

Changed the autofill bubble to have white background, black text, and
to be multiline if it is wider than two of the four columns in the UI
grid.

BUG=305378, 315966
R=isherman@chromium.org

Review URL: https://codereview.chromium.org/82513003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236749 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236749