Fix win64 build error

R=abarth@chromium.org
TBR=abarth@chromium.org

Review URL: https://codereview.chromium.org/75623002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235855 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235855