Clients that request the selection services menu after WebKit2 will get one with...

Clients that request the selection services menu after WebKit2 will get one with different metrics than otherwise
https://bugs.webkit.org/show_bug.cgi?id=135765
<rdar://problem/17962180>

Reviewed by Brady Eidson.

* UIProcess/mac/WebContextMenuProxyMac.mm:
(WebKit::WebContextMenuProxyMac::setupServicesMenu):
The menu is cached between clients, but we make adjustments to it.
We should copy it before adjusting.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@172364 268f45cc-cd09-0410-ab3c-d52691b4dbfc