Issue 3958 - Fixed initialization race condition when Adblock Plus is updated

lib/child/main.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
  */
 
-require("child/elemHide");
-require("child/contentPolicy");
-require("child/contextMenu");
-require("child/dataCollector");
-require("child/cssProperties");
-require("child/subscribeLinks");
+let {port} = require("messaging");
+
+// Only initialize after receiving a "response" to a dummy message - this makes
+// sure that on update the old version has enough time to receive and process
+// the shutdown message.
+port.emitWithResponse("ping").then(() =>

[Thomas Greiner, 2016/04/20 14:38:35]

Where is the code that responds to the "ping" event? I could only find such
handlers in the adblockplustests repository.

[Wladimir Palant, 2016/04/20 14:41:40]

There is none, we don't need a response. Or, if you prefer, the messaging module
sends an empty response because there are no handlers for this message.

+{
+  require("child/elemHide");
+  require("child/contentPolicy");
+  require("child/contextMenu");
+  require("child/dataCollector");
+  require("child/cssProperties");
+  require("child/subscribeLinks");
+});