Migrate test block 7 to Dart 2.0.

tests/corelib_2/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) {
+  } catch (e, stackTrace) {
     hasThrown = true;
-    var trace = e.stackTrace.toString();
+    var trace = 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);
 }