Limit number of service instances passed to onServiceList listeners.

chrome/common/extensions/api/mdns.idl

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Use the <code>chrome.mdns</code> API to discover services over mDNS.
 // This comprises a subset of the features of the NSD spec:
 // http://www.w3.org/TR/discovery-api/
 namespace mdns {
 
   // Represents a mDNS/DNS-SD service.
   dictionary MDnsService {
     // The service name of an mDNS advertised service,
     // <instance_name>.<service_type>.
     DOMString serviceName;
 
     // The host:port pair of an mDNS advertised service.
     DOMString serviceHostPort;
 
     // The IP address of an mDNS advertised service.
     DOMString ipAddress;
 
     // Metadata for an mDNS advertised service.
     DOMString[] serviceData;
   };
 
+  interface Properties {
+    // The maximum number of service instances that will be included in
+    // onServiceList events.  If more instances are available, they may be
+    // truncated from the onServiceList event.
+    [value=64] static long maxServiceInstancesPerEvent();
+  };
+
   interface Events {
     // Event fired to inform clients of the current complete set of known
     // available services. Clients should only need to store the list from the
     // most recent event. The service type that the extension is interested in
     // discovering should be specified as the event filter with the
     // 'serviceType' key. Not specifying an event filter will not start any
     // discovery listeners.
     [supportsFilters=true, maxListeners=10] static void onServiceList(MDnsService[] services);
   };
 };