Revert r148503

It caused a memory size regression specific to Mac that I never got a handle on.

BUG=232419
TBR=eseidel@chromium.org

Review URL: https://codereview.chromium.org/21490002

git-svn-id: svn://svn.chromium.org/blink/trunk@155396 bbb929c8-8fbe-4397-9dbb-9b2b20218538