Fix source position for stack traces with optimized top function.

tests/language/stack_overflow_stacktrace_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.
+// Dart program testing stack overflow.
+
+class StackOverflowTest {
+
+  static void curseTheRecurse(a, b, c) {
+    curseTheRecurse(b, c, a);
+  }
+
+  static void testMain() {
+    bool exceptionCaught = false;
+    try {
+      curseTheRecurse(1, 2, 3);
+    } on StackOverflowError catch (e, stacktrace) {
+      String s = stacktrace.toString();
+      Expect.equals(-1, s.indexOf("-1:-1"));
+      exceptionCaught = true;
+    }
+    Expect.equals(true, exceptionCaught);
+  }
+}
+
+main() {
+  StackOverflowTest.testMain();
+}