Bug 860849 - Fix 'Illegal Value' error in marionette. r=jgriffin, a=test-only

testing/marionette/marionette-elements.js

@@ -41,7 +41,6 @@ function ElementException(msg, num, stack) {
   this.stack = stack;
 }
 
-/* NOTE: Bug 736592 has been created to replace seenItems with a weakRef map */
 this.ElementManager = function ElementManager(notSupported) {
   this.searchTimeout = 0;
   this.seenItems = {};
@@ -72,10 +71,17 @@ ElementManager.prototype = {
   */
   addToKnownElements: function EM_addToKnownElements(element) {
     for (let i in this.seenItems) {
-      if (XPCNativeWrapper(this.seenItems[i].get()) == XPCNativeWrapper(element)) {
+      let foundEl = this.seenItems[i].get();
+      if (foundEl) {
+        if (XPCNativeWrapper(foundEl) == XPCNativeWrapper(element)) {
           return i;
         }
       }
+      else {
+        //cleanup reference to GC'd element
+        delete this.seenItems[i];
+      }
+    }
     var id = uuidGen.generateUUID().toString();
     this.seenItems[id] = Components.utils.getWeakReference(element);
     return id;
@@ -99,7 +105,7 @@ ElementManager.prototype = {
     }
     el = el.get();
     // use XPCNativeWrapper to compare elements; see bug 834266
-    if (!(XPCNativeWrapper(el).ownerDocument == XPCNativeWrapper(win).document)) {
+    if (!el || !(XPCNativeWrapper(el).ownerDocument == XPCNativeWrapper(win).document)) {
       throw new ElementException("Stale element reference", 10, null);
     }
     return el;
@@ -137,11 +143,6 @@ ElementManager.prototype = {
           result = null;
         }
         else if (val.nodeType == 1) {
-          for(let i in this.seenItems) {
-            if (this.seenItems[i].get() == val) {
-              result = {'ELEMENT': i};
-            }
-          }
           result = {'ELEMENT': this.addToKnownElements(val)};
         }
         else {