Make env_chromium_unittest compile on windows

Apparently clang doesn't mind the extra qualifier.

Review URL: https://codereview.chromium.org/27620002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@229379 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 229379