Revert 230577 "Perf experiment (to be reverted): use system mall..."

> Perf experiment (to be reverted): use system malloc on Mac.
> 
> BUG=310744
> R=abarth@chromium.org
> TBR=abarth@chromium.org
> 
> Review URL: https://codereview.chromium.org/35423009

TBR=cevans@chromium.org

Review URL: https://codereview.chromium.org/39543004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@230680 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 230680