Make DepotToLocalPath() and LocalToDepotPath() not static. It is necessary for a subsequent change since I need to factor out it's SCM assumption.

Review URL: http://codereview.chromium.org/113933

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@17091 0039d316-1c4b-4281-b951-d872f2087c98