Fix a bug where breakpoints where not getting properly deleted.

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 257 matching lines @@
     expect(frames.length, greaterThanOrEqualTo(1));
 
     Frame top = frames[0];
     Script script = await top.location.script.load();
     int actualLine = script.tokenToLine(top.location.tokenPos);
     if (actualLine != line) {
       var sb = new StringBuffer();
       sb.write("Expected to be at line $line but actually at line $actualLine");
       sb.write("\nFull stack trace:\n");
       for (Frame f in stack['frames']) {
-        sb.write(" $f\n");
+        sb.write(" $f [${await f.location.getLine()}]\n");
       }
       throw sb.toString();
     }
   };
 }
 
 
 Future<Isolate> resumeIsolate(Isolate isolate) {
   Completer completer = new Completer();
   isolate.vm.getEventStream(VM.kDebugStream).then((stream) {
@@ skipping 109 matching lines @@
       }, onError: (e, st) {
         process.requestExit();
         if (!_isWebSocketDisconnect(e)) {
           print('Unexpected exception in service tests: $e $st');
           throw e;
         }
       });
     });
   }
 }