Add end-to-end test for consistency in source map file and js file.

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);
+    });
+  }));
+}