Issue 2877 - Element Hiding Helper causes tab to crash when selecting some elements

lib/aardvark.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/.
  */
 
 let {Prefs} = require("prefs");
 
 // Make sure to stop selection when we are uninstalled
 onShutdown.add(() => Aardvark.quit());
 
 // To be replaced when selection starts
 function E(id) {return null;}
 
+let messageCounter = 0;
+
 /*********************************
  * Minimal element creation code *
  *********************************/
 
 function createElement(doc, tagName, attrs, children)
 {
   let el = doc.createElement(tagName);
   if (attrs)
     for (let key in attrs)
       el.setAttribute(key, attrs[key]);
@@ skipping 558 matching lines @@
     this.boxElem = null;
     E = id => null;
     return false;
   },
 
   select: function(elem)
   {
     if (!elem)
       return false;
 
+    let messageId = ++messageCounter;
+    let callback = (message) =>
+    {
+      let response = message.data;
+      if (response.messageId != messageId)
+        return;
+
+      this.browser.selectedBrowser.messageManager.removeMessageListener(
+        "ElemHideHelper:GetNodeInfo:Response",
+        callback
+      );
+
+      if (!response.nodeData)
+        return;
+
+      this.window.openDialog("chrome://elemhidehelper/content/composer.xul",
+          "_blank", "chrome,centerscreen,resizable,dialog=no", response);
+      this.quit();
+    };
+
+    this.browser.selectedBrowser.messageManager.addMessageListener(
+      "ElemHideHelper:GetNodeInfo:Response",
+      callback
+    );
     this.browser.selectedBrowser.messageManager.sendAsyncMessage(
       "ElemHideHelper:GetNodeInfo",
-      null,
+      messageId,
       {
-        element: elem,
-        callback: (response) =>
-        {
-          response = JSON.parse(response);
-          if (!response.nodeData)
-            return;
-
-          this.window.openDialog("chrome://elemhidehelper/content/composer.xul",
-              "_blank", "chrome,centerscreen,resizable,dialog=no", response);
-          this.quit();
-        }
+        element: elem
       }
     );
     return false;
   },
 
   blinkElement: function(elem)
   {
     if (!elem)
       return false;
 
@@ skipping 161 matching lines @@
     // Show help box
     helpBox.showPopup(this.browser, -1, -1, "tooltip", "topleft", "topleft");
     return true;
   }
 }
 
 // Makes sure event handlers like Aardvark.onKeyPress always have the correct
 // this pointer set.
 for (let method of ["onMouseClick", "onMouseScroll", "onKeyPress", "onPageHide", "onMouseMove", "onAfterPaint", "quit"])
   Aardvark[method] = Aardvark[method].bind(Aardvark);