Page Cache should support pages with frames.

Reviewed by Sam Weinig.

- Re-factor all remaining page cache code out of DocumentLoader, as CachedPage/CacheFrame loads
  are solely the responsibility of FrameLoader.
- Enhance some page cache related Logging to help development.

* inspector/InspectorController.cpp:
(WebCore::InspectorController::didCommitLoad):
(WebCore::InspectorController::identifierForInitialRequest):

* loader/DocumentLoader.cpp:
(WebCore::DocumentLoader::DocumentLoader):
* loader/DocumentLoader.h:

* loader/FrameLoader.cpp:
(WebCore::FrameLoader::FrameLoader):
(WebCore::FrameLoader::commitProvisionalLoad):
(WebCore::FrameLoader::continueLoadAfterWillSubmitForm):
(WebCore::FrameLoader::loadProvisionalItemFromCachedPage):
* loader/FrameLoader.h:
(WebCore::FrameLoader::isLoadingFromCachedPage):



git-svn-id: http://svn.webkit.org/repository/webkit/trunk@47407 268f45cc-cd09-0410-ab3c-d52691b4dbfc