Unreviewed, rolling out r167501.
https://bugs.webkit.org/show_bug.cgi?id=131913

It broke DYEBench (Requested by mhahnenberg on #webkit).

Reverted changeset:

"Deleting properties poisons objects"
https://bugs.webkit.org/show_bug.cgi?id=131551
http://trac.webkit.org/changeset/167501

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@167564 268f45cc-cd09-0410-ab3c-d52691b4dbfc