[GTK] Use the same DNS prefetching path than the other ports.

[GTK] Use the same DNS prefetching path than the other ports.
https://bugs.webkit.org/show_bug.cgi?id=80997

Reviewed by Martin Robinson.

This patch basically reverts r56128. There is no need to add an
special code path for GTK+ DNS pre-fetching because the main
reason to do that (some potential changes in libsoup) is not
going to happen. It also reduces the amount of DNS queries by
adding a NULL hostname check.

No need for new tests as this just moves code around.

* GNUmakefile.list.am:
* html/HTMLAnchorElement.cpp:
(WebCore::HTMLAnchorElement::parseAttribute):
* html/HTMLLinkElement.cpp:
* loader/LinkLoader.cpp:
(WebCore::LinkLoader::loadLink):
* page/Chrome.cpp:
(WebCore::Chrome::mouseDidMoveOverElement):
* platform/network/DNS.h:
(WebCore):
* platform/network/ResourceHandle.cpp:
* platform/network/ResourceHandle.h:
(ResourceHandle):
* platform/network/chromium/DNSChromium.cpp:
* platform/network/soup/DNSSoup.cpp: restored.
(WebCore):
(WebCore::prefetchDNS):
* platform/network/soup/ResourceHandleSoup.cpp:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@110669 268f45cc-cd09-0410-ab3c-d52691b4dbfc