Unreviewed, rolling out r177712 and r177717.
https://bugs.webkit.org/show_bug.cgi?id=139944

Caused flaky assertion failures (Requested by ap on #webkit).

Reverted changesets:

"[iOS] Log better using FeatureCounter why PageCache is
failing due to pruned resources"
https://bugs.webkit.org/show_bug.cgi?id=139921
http://trac.webkit.org/changeset/177712

"Unreviewed, fix build warning after r177712"
http://trac.webkit.org/changeset/177717

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@177735 268f45cc-cd09-0410-ab3c-d52691b4dbfc