Remove redundancy in source map entries.

tests/compiler/dart2js/source_map_d2js_consistency_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.
-
-import 'dart:async';
-import 'dart:io';
-import 'package:async_helper/async_helper.dart';
-
-import 'source_map_consistency_helper.dart';
-import '../../../sdk/lib/_internal/compiler/implementation/dart2js.dart' as entry;
-
-void main() {
-  asyncTest(() => createTempDir().then((Directory tmpDir) {
-    print('Compiling tests/compiler/dart2js/exit_code_helper.dart');
-    Future result =
-          entry.internalMain(['tests/compiler/dart2js/exit_code_helper.dart',
-                              '-o${tmpDir.path}/out.js',
-                              '--library-root=sdk']);
-      return result.then((_) {
-        Uri uri =
-            new Uri.file('${tmpDir.path}/out.js', windows: Platform.isWindows);
-        checkConsistency(uri);
-
-        print("Deleting '${tmpDir.path}'.");
-        tmpDir.deleteSync(recursive: true);
-      });
-  }));
-}