Add stackTrace to Error object.

tests/corelib/error_stack_trace2_test.dart

+// Copyright (c) 2013, 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 "package:expect/expect.dart";
+
+var cyclicStatic = cyclicStatic + 1;
+
+cyclicInitialization() {
+  return cyclicStatic;
+}
+
+main() {
+  bool hasThrown = false;
+  try {
+    cyclicStatic + 1;
+  } catch(e) {
+    hasThrown = true;
+    Expect.isTrue(e.stackTrace is StackTrace,
+                  "$e doesn't have a non-null stack trace");
+  }
+  Expect.isTrue(hasThrown);
+}