[EXPERIMENT] [MacViews] Enable and handle the profile switcher.
BrowserNonClientFrameView uses NewAvatarButton to implement the profile
switcher. However, the button's behavior is handled in BNCFV's
subclasses because they have different layout and hit-test logic. This
CL adds the necessary logic to BrowserNonClientFrameViewMac.
BUG=
565989
patch from issue 1517073002 at patchset 80001 (
http://crrev.com/1517073002#ps80001)