Issue 2816 - Restore Preview functionality

chrome/content/frameScript.js

 /*
  * This Source Code is subject to the terms of the Mozilla Public License
  * version 2.0 (the "License"). You can obtain a copy of the License at
  * http://mozilla.org/MPL/2.0/.
  */
 
 (function()
 {
   const Cu = Components.utils;
 
   let rand = Components.stack.filename.replace(/.*\?/, "");
   let module = "chrome://elemhidehelper/content/actor.jsm?" + rand;
-  let {shutdown, getNodeInfo} = Cu.import(module, {});
+  let {shutdown, getNodeInfo, togglePreview, forgetNode} = Cu.import(module, {});
 
   addMessageListener("ElemHideHelper:Shutdown", onShutdown);
   addMessageListener("ElemHideHelper:GetNodeInfo", onGetNodeInfo);
+  addMessageListener("ElemHideHelper:Preview", onTogglePreview);
 
   function onShutdown()
   {
     shutdown();
     Cu.unload(module);
     removeMessageListener("ElemHideHelper:Shutdown", onShutdown);
     removeMessageListener("ElemHideHelper:GetNodeInfo", onGetNodeInfo);
+    removeMessageListener("ElemHideHelper:Preview", onTogglePreview);
   }
 
   function onGetNodeInfo(message)
   {
-    let info = getNodeInfo(message.objects.element);
-    message.objects.callback(info.nodeData, info.host);
+    let nodeInfo = getNodeInfo(message.objects.element);
+    message.objects.callback(JSON.stringify(nodeInfo));

[Wladimir Palant, 2015/07/30 13:13:22]

Strictly speaking I am fixing an issue of the previous change here - it was
passing an object to the callback here. The callback is a CPOW
(https://developer.mozilla.org/en-US/Firefox/Multiprocess_Firefox/Cross_Proces...)
meaning that when we call it complex parameters won't be passed as structured
clones - they will rather become CPOWs themselves. This caused lots of
unnecessary cross-process traffic and console warnings, something that we can
completely avoid by passing a string.

+  }
+
+  function onTogglePreview(message)
+  {
+    togglePreview(message.data.nodeID, message.data.stylesheetData);
+    if (message.data.forgetNode)
+      forgetNode(message.data.nodeID);
   }
 })();