Reviewed by Adam Barth.

        Factor PageCache functionality out of FrameLoader and into
        PageCache itself.

        https://bugs.webkit.org/show_bug.cgi?id=39382

        Refactor only, so no new tests.

        * history/PageCache.cpp:
        (WebCore::pageCacheLogPrefix):
        (WebCore::pageCacheLog):
        (WebCore::logCanCacheFrameDecision):
        (WebCore::logCanCachePageDecision):
        (WebCore::PageCache::canCachePageContainingThisFrame):
        (WebCore::PageCache::canCache):
        (WebCore::PageCache::add):
        (WebCore::PageCache::get):
        * history/PageCache.h:
        * loader/DocumentLoader.cpp:
        (WebCore::DocumentLoader::commitIfReady):
        * loader/FrameLoader.cpp:
        (WebCore::FrameLoader::commitProvisionalLoad):
        (WebCore::FrameLoader::prepareForCachedPageRestore):
        (WebCore::FrameLoader::continueLoadAfterNavigationPolicy):
        (WebCore::FrameLoader::loadProvisionalItemFromCachedPage):
        (WebCore::FrameLoader::navigateToDifferentDocument):
        * loader/FrameLoader.h:
        (WebCore::FrameLoader::quickRedirectComing):
        * svg/graphics/SVGImage.cpp:
        (WebCore::SVGImage::dataChanged):


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@60688 268f45cc-cd09-0410-ab3c-d52691b4dbfc