Remove an unused field found by scythe.

R=pkasting@chromium.org, vandebo@chromium.org

Review URL: https://codereview.chromium.org/141953005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245656 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245656