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

runtime/vm/json_stream.h

Index: runtime/vm/json_stream.h
diff --git a/runtime/vm/json_stream.h b/runtime/vm/json_stream.h
index 92cbc4e240bf657a9cf28469c1cb41ffb3bca39f..239c4e76f3241cd43f0523d3494b2fd010121188 100644
--- a/runtime/vm/json_stream.h
+++ b/runtime/vm/json_stream.h
@@ -126,6 +126,10 @@ class JSONStream : ValueObject {
   // Append |serialized_object| to the stream.
   void AppendSerializedObject(const char* serialized_object);
 
+  // Append |serialized_object| to the stream with |property_name|.
+  void AppendSerializedObject(const char* property_name,
+                              const char* serialized_object);
+
  private:
   void Clear();
   void PostNullReply(Dart_Port port);