Partially revert r168100

In r168100, I mis-committed an unnecessary change to wtf/ to fix compile failure.
(The wtf/ change became unnecessary because the compile failure was fixed
in https://codereview.chromium.org/182733004/.)
This CL reverts the wtf/ part of r168100.

TBR=tkent
NOTRY=true

Review URL: https://codereview.chromium.org/176883010

git-svn-id: svn://svn.chromium.org/blink/trunk@168121 bbb929c8-8fbe-4397-9dbb-9b2b20218538