Merge MainResourceLoader's SubstituteData loading + others into DocumentLoader
https://bugs.webkit.org/show_bug.cgi?id=112722

Part of the ongoing effort to merge MainResourceLoader entirely
into DocumentLoader.

Reviewed by Antti Koivisto.

No new tests, refactor only.

* loader/DocumentLoader.cpp:
(WebCore::DocumentLoader::mainReceivedError): Moved from MainResourceLoader::receivedError
    and the failure case in MainResourceLoader::notifyFinished.
(WebCore::DocumentLoader::stopLoading):
(WebCore::DocumentLoader::finishedLoading):
(WebCore::DocumentLoader::handleSubstituteDataLoadNow): Moved from MainResourceLoader.
(WebCore::DocumentLoader::startDataLoadTimer): Moved from MainResourceLoader.
(WebCore::DocumentLoader::handleSubstituteDataLoadSoon): Moved from MainResourceLoader.
(WebCore::DocumentLoader::willSendRequest):
(WebCore::DocumentLoader::continueAfterNavigationPolicy):
(WebCore::DocumentLoader::responseReceived):
(WebCore::DocumentLoader::receivedData):
(WebCore::DocumentLoader::startLoadingMainResource): Most of MainResourceLoader::load
    moved here.
(WebCore::DocumentLoader::cancelMainResourceLoad): MainResourceLoader::cancel
    moved here.
* loader/DocumentLoader.h:
* loader/MainResourceLoader.cpp:
(WebCore::MainResourceLoader::notifyFinished):
(WebCore::MainResourceLoader::reportMemoryUsage):
(WebCore::MainResourceLoader::load):
(WebCore::MainResourceLoader::identifier):
* loader/MainResourceLoader.h:


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146239 268f45cc-cd09-0410-ab3c-d52691b4dbfc