Fix a crash.

test/package_root_info_test.dart

Index: test/package_root_info_test.dart
diff --git a/test/package_root_info_test.dart b/test/package_root_info_test.dart
index c0edba6e5d67fc3666e6f53a3bcb0867a7107798..f05f20c10376f0d3f5e918d0dc3823b279609ed0 100644
--- a/test/package_root_info_test.dart
+++ b/test/package_root_info_test.dart
@@ -22,6 +22,12 @@ void main() {
       expect(resolver.packageRoot, equals(Uri.parse("file:///foo/bar/")));
     });
 
+    test("with a URI without a path component", () {
+      var resolver =
+          new SyncPackageResolver.root(Uri.parse("http://localhost:1234"));
+      expect(resolver.packageRoot, equals(Uri.parse("http://localhost:1234/")));
+    });
+
     test("with an invalid URI type", () {
       expect(() => new SyncPackageResolver.root(12), throwsArgumentError);
     });