Minor clean-up in base/guid.*

BUG=None
R=thakis@chromium.org

Review URL: https://codereview.chromium.org/24767002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225681 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225681