Add dart:developer.postEvent for posting events to the service protocol from Dart code

runtime/lib/developer.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.
 
 import 'dart:isolate';
 
 patch bool debugger({bool when: true,
                      String message}) native "Developer_debugger";
 
 patch Object inspect(Object object) native "Developer_inspect";
@@ skipping 34 matching lines @@
 
 _log(String message,
      int timestamp,
      int sequenceNumber,
      int level,
      String name,
      Zone zone,
      Object error,
      StackTrace stackTrace) native "Developer_log";
 
+patch void _postEvent(String eventKind, String eventData)
+    native "Developer_postEvent";
+
 patch ServiceExtensionHandler _lookupExtension(String method)
     native "Developer_lookupExtension";
 
 patch _registerExtension(String method, ServiceExtensionHandler handler)
     native "Developer_registerExtension";
 
 // This code is only invoked when there is no other Dart code on the stack.
 _runExtension(ServiceExtensionHandler handler,
               String method,
               List<String> parameterKeys,
@@ skipping 62 matching lines @@
     sb.write('"result":');
   }
   sb.write('${response._toString()},');
   if (id is String) {
     sb.write('"id":"$id"}');
   } else {
     sb.write('"id":$id}');
   }
   replyPort.send(sb.toString());
 }