Fix crash when accessing automation node from stale AX tree

chrome/renderer/resources/extensions/automation/automation_node.js

Index: chrome/renderer/resources/extensions/automation/automation_node.js
diff --git a/chrome/renderer/resources/extensions/automation/automation_node.js b/chrome/renderer/resources/extensions/automation/automation_node.js
index 1598c6f9b0b8add00d770d08aaf8fed9d923008b..5e96405fd1cb408f2cc7fccc639c229a7b995ff0 100644
--- a/chrome/renderer/resources/extensions/automation/automation_node.js
+++ b/chrome/renderer/resources/extensions/automation/automation_node.js
@@ -757,7 +757,14 @@ AutomationRootNodeImpl.prototype = {
   axNodeDataCache_: null,
 
   get id() {
-    return GetRootID(this.treeID);
+    var result = GetRootID(this.treeID);
+
+    // Don't return undefined, because the id is often passed directly
+    // as an argument to a native binding that expects only a valid number.
+    if (result === undefined)
+      return -1;
+
+    return result;
   },
 
   get: function(id) {