Introduce a WorkQueueMessageReceiver class as a replacement for QueueClient
https://bugs.webkit.org/show_bug.cgi?id=109612

Reviewed by Andreas Kling.

* Platform/CoreIPC/Connection.cpp:
(CoreIPC::Connection::addWorkQueueMessageReceiver):
(CoreIPC):
(CoreIPC::Connection::removeWorkQueueMessageReceiver):
(CoreIPC::Connection::addWorkQueueMessageReceiverOnConnectionWorkQueue):
(CoreIPC::Connection::removeWorkQueueMessageReceiverOnConnectionWorkQueue):
* Platform/CoreIPC/Connection.h:
(Connection):

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@142672 268f45cc-cd09-0410-ab3c-d52691b4dbfc