Update pkg/path to use "package:" imports.

pkg/path/test/path_posix_test.dart

Index: pkg/path/test/path_posix_test.dart
diff --git a/pkg/path/test/path_posix_test.dart b/pkg/path/test/path_posix_test.dart
index b917e93ac46c33b60ec04f5815b779e99b3c0360..e1c39421dd7adcfd5919e2819ca2f71cb5f6b824 100644
--- a/pkg/path/test/path_posix_test.dart
+++ b/pkg/path/test/path_posix_test.dart
@@ -6,9 +6,8 @@ library path_test;
 
 import 'dart:io' as io;
 
-// TODO(rnystrom): Use "package:" path when #7491 is fixed.
-import '../../unittest/lib/unittest.dart';
-import '../lib/path.dart' as path;
+import 'package:unittest/unittest.dart';
+import 'package:path/path.dart' as path;
 
 main() {
   var builder = new path.Builder(style: path.Style.posix, root: '/root/path');