[Mac] Do not redraw the status bubble if nothing has changed.
[Mac] Do not redraw the status bubble if nothing has changed.

BUG=None
TEST=No visible impact.  Status bubble should look exactly the same as before when moving the mouse around.
Review URL: http://codereview.chromium.org/669179

git-svn-id: http://src.chromium.org/svn/trunk/src@40766 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 6270e58f6dce36885b4c1d1261b81142d22ec671
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser