Support piping log data over the service protocol

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 219 matching lines @@
         subscription.cancel();
         completer.complete();
       }
     });
   });
   isolate.resume();
   return completer.future;
 }
 
 
+Future resumeAndAwaitEvent(Isolate isolate, stream, onEvent) async {
+  Completer completer = new Completer();
+  var sub;
+  sub = await isolate.vm.listenEventStream(
+    stream,
+    (ServiceEvent event) {
+      var r = onEvent(event);
+      if (r is! Future) {
+        r = new Future.value(r);
+      }
+      r.then((x) => sub.cancel().then((_) {
+        completer.complete();
+      }));
+    });
+  await isolate.resume();
+  return completer.future;
+}
+
+IsolateTest resumeIsolateAndAwaitEvent(stream, onEvent) {
+  return (Isolate isolate) async =>
+      resumeAndAwaitEvent(isolate, stream, onEvent);
+}
+
+
 Future<Class> getClassFromRootLib(Isolate isolate, String className) async {
   Library rootLib = await isolate.rootLibrary.load();
   for (var i = 0; i < rootLib.classes.length; i++) {
     Class cls = rootLib.classes[i];
     if (cls.name == className) {
       return cls;
     }
   }
   return null;
 }
@@ skipping 38 matching lines @@
       }, onError: (e, st) {
         process.requestExit();
         if (!_isWebSocketDisconnect(e)) {
           print('Unexpected exception in service tests: $e $st');
           throw e;
         }
       });
     });
   }
 }