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

runtime/vm/json_stream.cc

Index: runtime/vm/json_stream.cc
diff --git a/runtime/vm/json_stream.cc b/runtime/vm/json_stream.cc
index a69eede2b1fb4564fdf6c5dd12bb180524fd059f..4851875703cd3b4c12c6e552b63d2a039c1169fc 100644
--- a/runtime/vm/json_stream.cc
+++ b/runtime/vm/json_stream.cc
@@ -262,6 +262,13 @@ void JSONStream::AppendSerializedObject(const char* serialized_object) {
 }
 
 
+void JSONStream::AppendSerializedObject(const char* property_name,
+                                        const char* serialized_object) {
+  PrintCommaIfNeeded();
+  PrintPropertyName(property_name);
+  buffer_.AddString(serialized_object);
+}
+
 void JSONStream::Clear() {
   buffer_.Clear();
   open_objects_ = 0;