Bug 429732 - speed up highlighting by optimizing _getEditableNode. r=ehsan

toolkit/modules/Finder.jsm

@@ -613,19 +613,18 @@ Finder.prototype = {
   },
 
   /*
-   * For a given node, walk up it's parent chain, to try and find an
-   * editable node.
+   * For a given node returns its editable parent or null if there is none.
+   * It's enough to check if aNode is a text node and its parent's parent is
+   * instance of nsIDOMNSEditableElement.
    *
    * @param aNode the node we want to check
    * @returns the first node in the parent chain that is editable,
    *          null if there is no such node
    */
   _getEditableNode: function (aNode) {
-    while (aNode) {
-      if (aNode instanceof Ci.nsIDOMNSEditableElement)
-        return aNode.editor ? aNode : null;
-
-      aNode = aNode.parentNode;
+    if (aNode.nodeType === aNode.TEXT_NODE && aNode.parentNode && aNode.parentNode.parentNode &&
+        aNode.parentNode.parentNode instanceof Ci.nsIDOMNSEditableElement) {
+      return aNode.parentNode.parentNode;
     }
     return null;
   },