CTTE: ApplicationCacheHost always has a DocumentLoader.
<https://webkit.org/b/b/128435>

Have ApplicationCacheHost store the backpointer to its owning
DocumentLoader as a reference.

Reviewed by Sam Weinig.

* loader/DocumentLoader.cpp:
(WebCore::DocumentLoader::DocumentLoader):
(WebCore::DocumentLoader::startLoadingMainResource):
* loader/appcache/ApplicationCacheHost.cpp:
(WebCore::ApplicationCacheHost::ApplicationCacheHost):
(WebCore::ApplicationCacheHost::~ApplicationCacheHost):
(WebCore::ApplicationCacheHost::selectCacheWithoutManifest):
(WebCore::ApplicationCacheHost::selectCacheWithManifest):
(WebCore::ApplicationCacheHost::maybeLoadMainResource):
(WebCore::ApplicationCacheHost::maybeLoadFallbackForMainResponse):
(WebCore::ApplicationCacheHost::maybeLoadFallbackForMainError):
(WebCore::ApplicationCacheHost::failedLoadingMainResource):
(WebCore::ApplicationCacheHost::finishedLoadingMainResource):
(WebCore::ApplicationCacheHost::maybeLoadResource):
(WebCore::ApplicationCacheHost::maybeLoadFallbackForError):
(WebCore::ApplicationCacheHost::maybeLoadSynchronously):
(WebCore::ApplicationCacheHost::notifyDOMApplicationCache):
(WebCore::ApplicationCacheHost::stopDeferringEvents):
(WebCore::ApplicationCacheHost::scheduleLoadFallbackResourceFromApplicationCache):
(WebCore::ApplicationCacheHost::update):
(WebCore::ApplicationCacheHost::swapCache):
(WebCore::ApplicationCacheHost::abort):
(WebCore::ApplicationCacheHost::isApplicationCacheEnabled):
* loader/appcache/ApplicationCacheHost.h:
(WebCore::ApplicationCacheHost::documentLoader): Deleted.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@170807 268f45cc-cd09-0410-ab3c-d52691b4dbfc