Don't show the combined menu if there are no services available

Don't show the combined menu if there are no services available
https://bugs.webkit.org/show_bug.cgi?id=135846
<rdar://problem/17582099>

Reviewed by Enrica Casucci.

* WebProcess/WebPage/ServicesOverlayController.h:
Add a FIXME.

* WebProcess/WebPage/mac/ServicesOverlayController.mm:
(WebKit::ServicesOverlayController::determineActiveHighlight):
Don't allow a selection Highlight to become active if there is no
service available to handle it. Previously we showed the combined menu
with just phone numbers in it if any were detected.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@172484 268f45cc-cd09-0410-ab3c-d52691b4dbfc