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;
   };
 
+  callback GetMaxServiceInstancesPerEvent = void (long n);
+
+  /*
+  enum Constants {
+    MaxServiceInstancesPerEvent = 64
+    //static long getMaxServiceInstancesPerEvent ();
+  }
+  */
+  interface Functions {
+    // The maximum number of service instances that will be included in

[not at google - send to devlin, 2015/04/01 20:25:58]

Sorry for the delay with this review, but I'm adding support for constants here:
https://codereview.chromium.org/1051563002 after which you'd be able to write
this properly (if unfortunately syntactically) as:

interface Properties {
  // The maximum number...
  [value=64] static long maxServiceInstancesPerEvent();
}

pretty similar to what you have, just it'd be a property rather than a getter
(and therefore accessible synchronously).

Also, the typical style for constants has been MAX_SERVICE_INSTANCES_PER_EVENT.

Up to you whether you want to wait for that CL to go in I suppose, but consider
it.

[Red Daly, 2015/04/01 22:52:05]

That works for me except I'm trying to commit before Friday's branch.  If the
other CL lands before end of tomorrow, I can change this API accordingly.

[Red Daly, 2015/04/02 22:25:21]

Thanks for that - updated.  Please take another look.

Note that I didn't update to use the MAX_SERVICE_INSTANCES_PER_EVENT style
because I interpret your comment to mean the CAPS_STYLE is for C++ code.  I
think camelCase is the convention in JavaScript APIs.

[not at google - send to devlin, 2015/04/02 22:36:22]

AFAIK Caps is the style for web APIs, e.g. see the constants in KeyboardEvent.

[Red Daly, 2015/04/03 17:58:55]

Done.

+    // onServiceList events.  If more instances are available, they may be
+    // truncated from the onServiceList event.
+    static void getMaxServiceInstancesPerEvent (
+        GetMaxServiceInstancesPerEvent callback);
+  };
+
   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] static void onServiceList(MDnsService[] services);
   };
 };