Consolidate duplicate code for resloving URIs.

pkg/analyzer/test/file_system/memory_file_system_test.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.
 
 library analyzer.test.file_system.memory_file_system_test;
 
 import 'dart:async';
 import 'dart:core' hide Resource;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/file_system/memory_file_system.dart';
 import 'package:analyzer/src/generated/engine.dart' show TimestampedData;
 import 'package:analyzer/src/generated/source.dart';
+import 'package:analyzer/src/generated/utilities_dart.dart';
 import 'package:path/path.dart';
 import 'package:unittest/unittest.dart';
 import 'package:watcher/watcher.dart';
 
 import '../reflective_tests.dart';
 import '../utils.dart';
 
 main() {
   initializeTestEnvironment();
   runReflectiveTests(FileSystemExceptionTest);
@@ skipping 371 matching lines @@
 
   void test_fullName() {
     expect(source.fullName, '/foo/test.dart');
   }
 
   void test_hashCode() {
     source.hashCode;
   }
 
   void test_resolveRelative() {
-    Uri relative = source.resolveRelativeUri(new Uri.file('bar/baz.dart'));
+    Uri relative = resolveRelativeUri(source.uri, new Uri.file('bar/baz.dart'));
     expect(relative.path, '/foo/bar/baz.dart');
   }
 
   void test_resolveRelative_dart() {
     File file = provider.newFile('/sdk/lib/core/core.dart', '');
     Source source = file.createSource(Uri.parse('dart:core'));
-    Uri resolved = source.resolveRelativeUri(Uri.parse('int.dart'));
+    Uri resolved = resolveRelativeUri(source.uri, Uri.parse('int.dart'));
     expect(resolved.toString(), 'dart:core/int.dart');
   }
 
   void test_shortName() {
     expect(source.shortName, 'test.dart');
   }
 }
 
 @reflectiveTest
 class MemoryFileSourceNotExistingTest {
@@ skipping 21 matching lines @@
 
   void test_fullName() {
     expect(source.fullName, '/foo/test.dart');
   }
 
   void test_modificationStamp() {
     expect(source.modificationStamp, -1);
   }
 
   void test_resolveRelative() {
-    Uri relative = source.resolveRelativeUri(new Uri.file('bar/baz.dart'));
+    Uri relative = resolveRelativeUri(source.uri, new Uri.file('bar/baz.dart'));
     expect(relative.path, '/foo/bar/baz.dart');
   }
 
   void test_shortName() {
     expect(source.shortName, 'test.dart');
   }
 }
 
 @reflectiveTest
 class MemoryResourceProviderTest {
@@ skipping 173 matching lines @@
     return new Future.delayed(Duration.ZERO, computation);
   }
 
   _watchingFolder(String path, test(List<WatchEvent> changesReceived)) {
     Folder folder = provider.getResource(path);
     var changesReceived = <WatchEvent>[];
     folder.changes.listen(changesReceived.add);
     return test(changesReceived);
   }
 }