Disable source maps completely.

dart/tests/try/web/incremental_compilation_update_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 trydart.incremental_compilation_update_test;
 
 import 'dart:html';
 
 import 'dart:async' show
     Future;
@@ skipping 443 matching lines @@
   if (instance == null) {
     instance = new A();
   } else {
     instance = new B();
   }
   instance.m();
 }
 """,
             const <String>['Called B.m']),
     ],
+
+    // Test that source maps don't throw exceptions.
+    const <ProgramResult>[
+        const ProgramResult(
+            """
+main() {
+  print('a');
+}
+""",
+            const <String>['a']),
+
+        const ProgramResult(
+            """
+main() {
+  print('a');
+  print('b');
+  print('c');
+}
+""",
+            const <String>['a', 'b', 'c']),
+    ],
 ];
 
 void main() {
   listener.start();
 
   document.head.append(lineNumberStyle());
 
   return asyncTest(() => Future.forEach(tests, compileAndRun));
 }
 
@@ skipping 106 matching lines @@
   position: absolute;
   left: 0px;
   width: 3em;
   text-align: right;
   background-color: lightgoldenrodyellow;
 }
 ''');
   style.type = 'text/css';
   return style;
 }