Display isolate message queue in Observatory debugger

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 f894c712fedc1b5794c33d4624a46cd9df89dd76..c122bb787e24132a107acf53fd4ce4e6887c913d 100644
--- a/runtime/vm/json_stream.cc
+++ b/runtime/vm/json_stream.cc
@@ -273,6 +273,12 @@ void JSONStream::PrintValue(Metric* metric) {
 }
 
 
+void JSONStream::PrintValue(MessageQueue* queue) {
+  PrintCommaIfNeeded();
+  queue->PrintJSON(this);
+}
+
+
 void JSONStream::PrintValue(Isolate* isolate, bool ref) {
   PrintCommaIfNeeded();
   isolate->PrintJSON(this, ref);
@@ -342,6 +348,13 @@ void JSONStream::PrintProperty(const char* name, Metric* metric) {
   PrintValue(metric);
 }
 
+
+void JSONStream::PrintProperty(const char* name, MessageQueue* queue) {
+  PrintPropertyName(name);
+  PrintValue(queue);
+}
+
+
 void JSONStream::PrintProperty(const char* name, Isolate* isolate) {
   PrintPropertyName(name);
   PrintValue(isolate);