Change package scheduled_test to throw TestFailures rather than strings.

pkg/scheduled_test/lib/scheduled_process.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 scheduled_test.scheduled_process;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
@@ skipping 165 matching lines @@
       wrapFuture(pumpEventQueue().then((_) {
         if (currentSchedule.currentTask != _taskBeforeEnd) return;
         // If we're one task before the end was scheduled, wait for that task
         // to complete and pump the event queue so that _endExpected will be
         // set.
         return _taskBeforeEnd.result.then((_) => pumpEventQueue());
       }).then((_) {
         exitCodeCompleter.complete(exitCode);
 
         if (!_endExpected) {
-          throw "Process '$description' ended earlier than scheduled "
-            "with exit code $exitCode.";
+          fail("Process '$description' ended earlier than scheduled "
+               "with exit code $exitCode.");
         }
       }), "waiting to reach shouldExit() or kill() for process "
           "'$description'");
     });
   }
 
   /// Converts a stream of bytes to a stream of lines and returns that along
   /// with a [StreamCanceller] controlling it.
   Pair<Stream<String>, StreamCanceller> _lineStreamWithCanceller(
       Future<Stream<List<int>>> streamFuture) {
@@ skipping 146 matching lines @@
     schedule(() {
       _endExpected = true;
       return _exitCode.then((exitCode) {
         if (expectedExitCode != null) {
           expect(exitCode, equals(expectedExitCode));
         }
       });
     }, "waiting for process '$description' to exit");
   }
 }