Add sourceMaps option to $dart2js transformer.

sdk/lib/_internal/pub_generated/test/dart2js/omits_source_map_if_sourceMaps_false_test.dart

Index: sdk/lib/_internal/pub_generated/test/dart2js/omits_source_map_if_sourceMaps_false_test.dart
diff --git a/sdk/lib/_internal/pub_generated/test/dart2js/omits_source_map_if_sourceMaps_false_test.dart b/sdk/lib/_internal/pub_generated/test/dart2js/omits_source_map_if_sourceMaps_false_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..f777b911f59d2af3b7a2750de3de4343cffde523
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/test/dart2js/omits_source_map_if_sourceMaps_false_test.dart
@@ -0,0 +1,32 @@
+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 '../descriptor.dart' as d;
+import '../test_pub.dart';
+
+main() {
+  initConfig();
+  integration("omits source maps from a debug build if sourceMaps false", () {
+    d.dir(appPath, [d.pubspec({
+        'name': 'myapp',
+        'transformers': [{
+            '\$dart2js': {
+              'sourceMaps': false
+            }
+          }]
+      }),
+          d.dir(
+              "web",
+              [d.file("main.dart", "void main() => print('hello');")])]).create();
+
+    schedulePub(
+        args: ["build", "--mode", "debug"],
+        output: new RegExp(r'Built \d+ files to "build".'),
+        exitCode: 0);
+
+    d.dir(
+        appPath,
+        [d.dir('build', [d.dir('web', [d.nothing('main.dart.js.map')])])]).validate();
+  });
+}