Display isolate message queue in Observatory debugger

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 6c20d4facaa86daea9d5fbe23b29689b99dfee05..12bd79873538217b4bd99974912d12f632c5ed6f 100644
--- a/runtime/vm/json_stream.h
+++ b/runtime/vm/json_stream.h
@@ -17,6 +17,7 @@ class GrowableObjectArray;
 class Instance;
 class JSONArray;
 class JSONObject;
+class MessageQueue;
 class Metric;
 class Object;
 class ServiceEvent;
@@ -91,6 +92,7 @@ class JSONStream : ValueObject {
   void PrintValue(SourceBreakpoint* bpt);
   void PrintValue(const ServiceEvent* event);
   void PrintValue(Metric* metric);
+  void PrintValue(MessageQueue* queue);
   void PrintValue(Isolate* isolate, bool ref = true);
   bool PrintValueStr(const String& s, intptr_t limit);
 
@@ -108,6 +110,7 @@ class JSONStream : ValueObject {
   void PrintProperty(const char* name, const ServiceEvent* event);
   void PrintProperty(const char* name, SourceBreakpoint* bpt);
   void PrintProperty(const char* name, Metric* metric);
+  void PrintProperty(const char* name, MessageQueue* queue);
   void PrintProperty(const char* name, Isolate* isolate);
   void PrintPropertyName(const char* name);
   void PrintCommaIfNeeded();
@@ -183,6 +186,9 @@ class JSONObject : public ValueObject {
   void AddProperty(const char* name, Metric* metric) const {
     stream_->PrintProperty(name, metric);
   }
+  void AddProperty(const char* name, MessageQueue* queue) const {
+    stream_->PrintProperty(name, queue);
+  }
   void AddProperty(const char* name, Isolate* isolate) const {
     stream_->PrintProperty(name, isolate);
   }
@@ -234,6 +240,9 @@ class JSONArray : public ValueObject {
   void AddValue(Metric* metric) const {
     stream_->PrintValue(metric);
   }
+  void AddValue(MessageQueue* queue) const {
+    stream_->PrintValue(queue);
+  }
   void AddValueF(const char* format, ...) const PRINTF_ATTRIBUTE(2, 3);
 
  private: