Source positions for constructors and lots of async machinery

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 237 matching lines @@
     print("Checking we are at line $line");
 
     ServiceMap stack = await isolate.getStack();
     expect(stack.type, equals('Stack'));
 
     List<Frame> frames = stack['frames'];
     expect(frames.length, greaterThanOrEqualTo(1));
 
     Frame top = frames[0];
     Script script = await top.location.script.load();
-    if (script.tokenToLine(top.location.tokenPos) != line) {
+    int actualLine = script.tokenToLine(top.location.tokenPos);
+    if (actualLine != line) {
       var sb = new StringBuffer();
-      sb.write("Expected to be at line $line, but got stack trace:\n");
+      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");
       }
       throw sb.toString();
     }
   };
 }
 
 
 Future<Isolate> resumeIsolate(Isolate isolate) {
@@ skipping 109 matching lines @@
       }, onError: (e, st) {
         process.requestExit();
         if (!_isWebSocketDisconnect(e)) {
           print('Unexpected exception in service tests: $e $st');
           throw e;
         }
       });
     });
   }
 }