Insert debug step check at the beginning of a function.

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.
 // VMOptions=--compile_all --error_on_bad_type --error_on_bad_override --checked
 
 library test_helper;
 
 import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
@@ skipping 137 matching lines @@
   vm.getEventStream(streamId).then((stream) {
     var subscription;
     subscription = stream.listen((ServiceEvent event) {
       handler(event, subscription, completer);
     });
   });
   return completer.future;
 }
 
 
-Future<Isolate> hasStoppedAtBreakpoint(Isolate isolate) {
+Future<Isolate> hasStoppedAtBreakpoint(Isolate isolate) async {
+  await isolate.reload();  // Might have missed pauseEvent.
+
   if ((isolate.pauseEvent != null) &&
       (isolate.pauseEvent.kind == ServiceEvent.kPauseBreakpoint)) {
     // Already waiting at a breakpoint.
     print('Breakpoint reached');
     return new Future.value(isolate);
   }
 
   // Set up a listener to wait for breakpoint events.
   Completer completer = new Completer();
   isolate.vm.getEventStream(VM.kDebugStream).then((stream) {
@@ skipping 66 matching lines @@
       }, onError: (e, st) {
         process.requestExit();
         if (!_isWebSocketDisconnect(e)) {
           print('Unexpected exception in service tests: $e $st');
           throw e;
         }
       });
     });
   }
 }