Migrate test block 7 to Dart 2.0.

tests/corelib/error_stack_trace1_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";
-
-class A {
-  static Aa() => Ab();
-  static Ab() => Ac();
-  static Ac() => throw "abc";
-}
-
-class B {
-  static Ba() => Bb();
-  static Bb() => Bc();
-  static Bc() {
-    try {
-      A.Aa();
-    } catch (e) {
-      // This should produce a NoSuchMethodError.
-      var trace = e.stackTrace;
-    }
-  }
-}
-
-main() {
-  bool hasThrown = false;
-  try {
-    B.Ba();
-  } catch (e) {
-    hasThrown = true;
-    var trace = e.stackTrace.toString();
-    print(trace);
-    Expect.isTrue(trace.contains("Bc"));
-    Expect.isTrue(trace.contains("Bb"));
-    Expect.isTrue(trace.contains("Ba"));
-    Expect.isTrue(trace.contains("main"));
-  }
-  Expect.isTrue(hasThrown);
-}