Bug 1440022: Some infrastructure for testing broadcast_subscribe r=lina

MozReview-Commit-ID: 8Re4EGCSbmi

--HG--
extra : rebase_source : 8f851ce140f6e61816d002490de3b0af2fb5fe3d

dom/push/test/xpcshell/head.js

@@ -187,6 +187,7 @@ function MockWebSocket(originalURI, handlers = {}) {
   this._onUnregister = handlers.onUnregister;
   this._onACK = handlers.onACK;
   this._onPing = handlers.onPing;
+  this._onBroadcastSubscribe = handlers.onBroadcastSubscribe;
 }
 
 MockWebSocket.prototype = {
@@ -259,6 +260,13 @@ MockWebSocket.prototype = {
       }
       break;
 
+    case 'broadcast_subscribe':
+      if (typeof this._onBroadcastSubscribe != 'function') {
+        throw new Error('Unexpected broadcast_subscribe');
+      }
+      this._onBroadcastSubscribe(request);
+      break;
+
     default:
       throw new Error('Unexpected message: ' + messageType);
     }