Add DiscoveryNetworkMonitor implementation

chrome/common/extensions/api/dial.idl

 // Copyright (c) 2012 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.dial</code> API to discover devices that support DIAL.
 // Protocol specification: http://www.dial-multiscreen.org/
 namespace dial {
 
   // Represents a unique device that responded to a DIAL discovery request.
   dictionary DialDevice {
@@ skipping 20 matching lines @@
     // The contents of the Application-URL header in the response.
     DOMString appUrl;
 
     // The content of the response body.  This will be an XML document
     // (hopefully) conforming to section 2.3 of the UPnP spec.
     DOMString deviceDescription;
   };
 
   enum DialErrorCode {
     no_listeners,
+    // Deprecated.  Use onNetworkIdChanged instead.
     no_valid_network_interfaces,
+    // Deprecated.  Use onNetworkIdChanged instead.
     network_disconnected,
     cellular_network,
     socket_error,
     unknown
   };
 
   dictionary DialError {
     DialErrorCode code;
   };
 
   callback BooleanCallback = void (boolean result);
   callback DeviceDescriptionCallback = void (DialDeviceDescription result);
+  callback NetworkIdCallback = void (DOMString result);
 
   interface Functions {
 
     // Requests that DIAL discovery happen immediately.  The request may not be
     // honored as discovery may already be happening in the background.  The
     // callback is invoked with |true| if discovery was initiated or |false|
     // otherwise.
     static void discoverNow(BooleanCallback callback);
 
     // Fetches the device description for the DIAL device identified by
     // |deviceLabel|.  If successful, the callback is invoked with a
     // DialDeviceDescription containing the content of the device description.
     //
     // If unsuccessful, callback is invoked with |null| and lastError is set to
     // an error message.  If the error occurred during the HTTP fetch itself,
     // the message will begin with "HTTP XXX:" where XXX is the HTTP result
     // code.
     static void fetchDeviceDescription(DOMString deviceLabel,
                                        DeviceDescriptionCallback callback);
+
+    // Returns the current discovery network identifier.  See the documentation
+    // for onNetworkIdChanged for details.
+    static void getNetworkId(NetworkIdCallback callback);
   };
 
   interface Events {
 
     // Event fired to inform clients of the current, complete set of responsive
     // devices.  Clients should only need to store the list from the most recent
     // event.  May be fired in response to multiple circumstances:
     //
     // (1) The DIAL service refreshed its device list through periodic polling.
     // (2) A client invoked discoverNow().
     // (3) An event happened that should invalidate the device list
     //     (e.g., a network interface went offline), in which case it is fired
     //     with an empty array.
     static void onDeviceList(DialDevice[] result);
 
     // Event fired to inform clients on errors during device discovery.
     static void onError(DialError error);
+
+    // Fired when the network being used for discovery has changed.  |networkId|
+    // contains a short signature combining information from network interface
+    // and WiFi network identifiers to identify the current set of networks
+    // being used for discovery.  This can be used by clients to clear and
+    // re-bootstrap device caches on a network change.
+    //
+    // |networkId| can take the following values:
+    // - "hex-string" is a hash-style signature of the set of active networks.
+    // - "disconnected" means there is no active network for discovery.
+    // - "unknown" means there is an active network, but its signature
+    //   cannot be determined.
+    //
+    // This event may be throttled to prevent it from firing too frequently; it
+    // is designed to be event-page friendly.
+    static void onNetworkIdChanged(DOMString networkId);
   };
 };