Only show breakpoints at possible breakpoint positions in Observatory.

runtime/observatory/tests/service/debugger_location_test.dart

 // Copyright (c) 2015, 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=--error_on_bad_type --error_on_bad_override
 
 import 'package:observatory/service_io.dart';
 import 'package:observatory/debugger.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 import 'dart:async';
@@ skipping 218 matching lines @@
       '[debugger_location_test.dart:]'));
 },
 
 // Complete script:line
 (Isolate isolate) async {
   var debugger = await initDebugger(isolate);
   var completions =
       await DebuggerLocation.complete(debugger,
                                       'debugger_location_test.dart:11');
   expect(completions.toString(), equals(
-      '[debugger_location_test.dart:11 ,'
-      ' debugger_location_test.dart:11:,'
-      ' debugger_location_test.dart:110 ,'
+      '[debugger_location_test.dart:110 ,'
       ' debugger_location_test.dart:110:,'
       ' debugger_location_test.dart:111 ,'
       ' debugger_location_test.dart:111:,'
       ' debugger_location_test.dart:112 ,'
       ' debugger_location_test.dart:112:,'
       ' debugger_location_test.dart:115 ,'
       ' debugger_location_test.dart:115:,'
       ' debugger_location_test.dart:116 ,'
       ' debugger_location_test.dart:116:,'
       ' debugger_location_test.dart:117 ,'
@@ skipping 28 matching lines @@
       ' debugger_location_test.dart:11:20 ,'
       ' debugger_location_test.dart:11:21 ,'
       ' debugger_location_test.dart:11:22 ,'
       ' debugger_location_test.dart:11:23 ,'
       ' debugger_location_test.dart:11:24 ]'));
 },
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeConcurrent: testFunction);