Revert 231757 "Enable people search by default."

> Enable people search by default.
> Leave a flag in to be able to disable it in case we want to turn the feature off for any reason.
> 
> R=xiyuan@chromium.org
> BUG=309695
> 
> Review URL: https://codereview.chromium.org/50143011

TBR=rkc@chromium.org

Review URL: https://codereview.chromium.org/51893003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@232212 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 232212