Don't use a special var descriptor for :async_op since it can now be either stack or context alloca…

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 231 matching lines @@
     expect(bpt is Breakpoint, isTrue);
   };
 }
 
 IsolateTest stoppedAtLine(int line) {
   return (Isolate isolate) async {
     print("Checking we are at line $line");
 
     ServiceMap stack = await isolate.getStack();
     expect(stack.type, equals('Stack'));
-    expect(stack['frames'].length, greaterThanOrEqualTo(1));
 
-    Frame top = stack['frames'][0];
-    print("We are at $top");
+    List<Frame> frames = stack['frames'];
+    expect(frames.length, greaterThanOrEqualTo(1));
+
+    Frame top = frames[0];
     Script script = await top.location.script.load();
-    expect(script.tokenToLine(top.location.tokenPos), equals(line));
+    if (script.tokenToLine(top.location.tokenPos) != line) {
+      var sb = new StringBuffer();
+      sb.write("Expected to be at line $line, but got stack trace:\n");
+      for (Frame f in stack['frames']) {
+        sb.write(" $f\n");
+      }
+      throw sb.toString();
+    }
   };
 }
 
 
 Future<Isolate> resumeIsolate(Isolate isolate) {
   Completer completer = new Completer();
   isolate.vm.getEventStream(VM.kDebugStream).then((stream) {
     var subscription;
     subscription = stream.listen((ServiceEvent event) {
       if (event.kind == ServiceEvent.kResume) {
@@ skipping 93 matching lines @@
       }, onError: (e, st) {
         process.requestExit();
         if (!_isWebSocketDisconnect(e)) {
           print('Unexpected exception in service tests: $e $st');
           throw e;
         }
       });
     });
   }
 }