[SOUP] ResourceHandleSoup should use async client callbacks when client uses async callbacks
https://bugs.webkit.org/show_bug.cgi?id=126006

Reviewed by Martin Robinson.

This fixes WebKit2 loader client unit tests when using the network
process.

* platform/network/ResourceHandle.cpp:
* platform/network/soup/ResourceHandleSoup.cpp:
(WebCore::doRedirect): Call willSendRequestAsync on the client
when usesAsyncCallbacks returns true.
(WebCore::nextMultipartResponsePartCallback): Call
didReceiveResponseAsync on the client when usesAsyncCallbacks
returns true.
(WebCore::sendRequestCallback): Ditto.
(WebCore::ResourceHandle::continueWillSendRequest): Empty
implementation for now because the default one asserts.
(WebCore::ResourceHandle::continueDidReceiveResponse): Ditto.
(WebCore::ResourceHandle::continueShouldUseCredentialStorage): Ditto.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@160961 268f45cc-cd09-0410-ab3c-d52691b4dbfc