Remove getCurrentDirectoryURL and getCurrentDirPath from directory_model.js.

This CL removes two methods which rely on URL and full paths, what is deprecated.

TEST=Tested manually.
BUG=328252

Review URL: https://codereview.chromium.org/101243003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243077 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243077