Track async causal stack traces

runtime/observatory/tests/service/test_helper.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.
 
 library test_helper;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 import 'package:observatory/service_io.dart';
@@ skipping 310 matching lines @@
             vm.verbose = verbose_vm;
             print('Running $name [$testIndex/$totalTests]');
             testIndex++;
             await test(isolate);
           }
         }
 
         await process.requestExit();
       }, onError: (error, stackTrace) {
         process.requestExit();
-        print('Unexpected exception in service tests: $error\n$stackTrace');
+        print('Unexpected exception in service tests: $error\n'
+              '${stackTrace.terse}');
         throw error;
       });
     });
   }
 }
 
 /// Runs [tests] in sequence, each of which should take an [Isolate] and
 /// return a [Future]. Code for setting up state can run before and/or
 /// concurrently with the tests. Uses [mainArgs] to determine whether
 /// to run tests or testee in this invokation of the script.
@@ skipping 87 matching lines @@
     new _ServiceTesterRunner().run(
         mainArgs: mainArgs,
         extraArgs: extraArgs,
         vmTests: tests,
         pause_on_start: pause_on_start,
         pause_on_exit: pause_on_exit,
         verbose_vm: verbose_vm,
         pause_on_unhandled_exceptions: pause_on_unhandled_exceptions);
   }
 }