Revert 165896 "Turn the setup of the oilpan heap infrastructure ..."

> Turn the setup of the oilpan heap infrastructure on by default.
> 
> In order to be able to ship certain simple modules using the heap
> infrastructure we need the infrastructure to be turned on by default.
> That way, ENABLE(OILPAN) controls only which parts of Blink are
> shipped with the objects in the traced heap.
> 
> BUG=
> 
> Review URL: https://codereview.chromium.org/142483004

TBR=ager@chromium.org

Review URL: https://codereview.chromium.org/131503014

git-svn-id: svn://svn.chromium.org/blink/trunk@165980 bbb929c8-8fbe-4397-9dbb-9b2b20218538