Optimize the message queue for many active ports with few messages.

runtime/vm/object_store.h

Index: runtime/vm/object_store.h
diff --git a/runtime/vm/object_store.h b/runtime/vm/object_store.h
index c46e5271d4ffa3c50e5324ff70d950803364030d..c216a90ede68bf2bb613c563dc7c852638092536 100644
--- a/runtime/vm/object_store.h
+++ b/runtime/vm/object_store.h
@@ -476,6 +476,13 @@ class ObjectStore {
     receive_port_create_function_ = function.raw();
   }
 
+  RawFunction* lookup_receive_port_function() const {
+    return lookup_receive_port_function_;
+  }
+  void set_lookup_receive_port_function(const Function& function) {
+    lookup_receive_port_function_ = function.raw();
+  }
+
   RawFunction* handle_message_function() const {
     return handle_message_function_;
   }
@@ -575,6 +582,7 @@ class ObjectStore {
   RawInstance* out_of_memory_;
   RawArray* keyword_symbols_;
   RawFunction* receive_port_create_function_;
+  RawFunction* lookup_receive_port_function_;
   RawFunction* handle_message_function_;
   RawObject** to() { return reinterpret_cast<RawObject**>(&keyword_symbols_); }