Add toUri and fromUri functions to pathos.

pkg/pathos/test/pathos_url_test.dart

Index: pkg/pathos/test/pathos_url_test.dart
diff --git a/pkg/pathos/test/pathos_url_test.dart b/pkg/pathos/test/pathos_url_test.dart
index b8c100f27afe4613a573dadec3824b86b2ee1f69..e28634c02a49dded87f59c17f099a5ea3abefc1a 100644
--- a/pkg/pathos/test/pathos_url_test.dart
+++ b/pkg/pathos/test/pathos_url_test.dart
@@ -625,4 +625,21 @@ main() {
     expect(builder.withoutExtension('a/b.c/'), 'a/b/');
     expect(builder.withoutExtension('a/b.c//'), 'a/b//');
   });
+
+
+  test('fromUri', () {
+    expect(builder.fromUri(Uri.parse('http://dartlang.org/path/to/foo')),
+        'http://dartlang.org/path/to/foo');
+    expect(builder.fromUri(Uri.parse('file:///path/to/foo')),
+        'file:///path/to/foo');
+    expect(builder.fromUri(Uri.parse('foo/bar')), 'foo/bar');
+  });
+
+  test('toUri', () {
+    expect(builder.toUri('http://dartlang.org/path/to/foo'),
+        Uri.parse('http://dartlang.org/path/to/foo'));
+    expect(builder.toUri('file:///path/to/foo'),
+        Uri.parse('file:///path/to/foo'));
+    expect(builder.fromUri('foo/bar'), Uri.parse('foo/bar'));
+  });
 }