Import tools/testing/dart/path.dart in tests that used to get this through utils.dart

tests/compiler/dart2js/frontend_checker.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Checks that dart2js produces the expected static type warnings and
 // compile-time errors for the provided multitests.
 
 import 'dart:async';
 
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 
 import 'memory_compiler.dart';
 
 import '../../../tools/testing/dart/multitest.dart'
     show ExtractTestsFromMultitest;
-import '../../../tools/testing/dart/utils.dart'
+import '../../../tools/testing/dart/path.dart'
     show Path;
 
 void check(List<String> testFiles,
            {List<String> arguments: const <String>[],
             List<String> options: const <String>[]}) {
   bool outcomeMismatch = false;
   bool verbose = arguments.contains('-v');
   var cachedCompiler;
   asyncTest(() => Future.forEach(testFiles, (String testFile) {
     Map<String, String> testSources = {};
@@ skipping 34 matching lines @@
             outcomeMismatch = true;
           }
         }
         cachedCompiler = compiler;
       });
     });
   }).then((_) {
     Expect.isFalse(outcomeMismatch, 'Outcome mismatch');
   }));
 }