Remove redundancy in source map entries.

tests/compiler/dart2js/source_map_pub_build_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:io';
-
-import 'package:path/path.dart' as path;
-import 'package:async_helper/async_helper.dart';
-
-import 'source_map_consistency_helper.dart';
-
-void main() {
-  asyncTest(() => createTempDir().then((Directory tmpDir) {
-    Directory sunflowerDir = new Directory.fromUri(
-        Platform.script.resolve('../../../samples/sunflower'));
-
-    print("Copying '${sunflowerDir.path}' to '${tmpDir.path}'.");
-    copyDirectory(sunflowerDir, tmpDir);
-    String ext = Platform.isWindows ? '.bat' : '';
-    String command = path.normalize(path.join(path.fromUri(Platform.script),
-                                              '../../../../sdk/bin/pub${ext}'));
-    String file = path.join(tmpDir.path, 'build/web/sunflower.dart.js');
-    print("Running '$command build --mode=debug' from '${tmpDir}'.");
-    return Process.run(command, ['build','--mode=debug'],
-        workingDirectory: tmpDir.path).then((process) {
-      print(process.stdout);
-      checkConsistency(new Uri.file(file, windows: Platform.isWindows));
-      print("Deleting '${tmpDir.path}'.");
-      tmpDir.deleteSync(recursive: true);
-    });
-  }));
-}