Add optional message to assert in Dart2js - continued

tests/compiler/dart2js/js_backend_cps_ir.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.
 
 // Test that the CPS IR code generator compiles programs and produces the
 // the expected output.
 
 import 'package:async_helper/async_helper.dart';
 import 'package:expect/expect.dart';
 import 'package:compiler/src/apiimpl.dart'
@@ skipping 61 matching lines @@
         String expectation = test.expectation;
         if (expectation != null) {
           String expected = test.expectation;
           String found = test.elementName == null
               ? getCodeForMain(compiler)
               : getCodeForMethod(compiler, test.elementName);
           if (expected != found) {
             Expect.fail('Expected:\n$expected\nbut found\n$found');
           }
         }
-      } catch (e) {
+      } catch (e, st) {
         print(e);
+        print(st);
         Expect.fail('The following test failed to compile:\n'
                     '${formatTest(files)}');
       }
     });
   }
 }