Automation API: Get rid of host node and get parent from C++ bindings instead

chrome/renderer/resources/extensions/automation_custom_bindings.js

Index: chrome/renderer/resources/extensions/automation_custom_bindings.js
diff --git a/chrome/renderer/resources/extensions/automation_custom_bindings.js b/chrome/renderer/resources/extensions/automation_custom_bindings.js
index 1038fd35ca2a55904117aef659f9fa85221c291d..2dbb93017e8b00d2d7188e42b8bfab5a851c3d2d 100644
--- a/chrome/renderer/resources/extensions/automation_custom_bindings.js
+++ b/chrome/renderer/resources/extensions/automation_custom_bindings.js
@@ -224,8 +224,6 @@ automationInternal.onChildTreeID.addListener(function(treeID,
       if (root.parent)
         return;
 
-      privates(root).impl.setHostNode(node);
-
       if (root.docLoaded) {
         privates(root).impl.dispatchEvent('loadComplete', 'page');
       }
@@ -234,8 +232,6 @@ automationInternal.onChildTreeID.addListener(function(treeID,
     });
 
     automationInternal.enableFrame(childTreeID);
-  } else {
-    privates(subroot).impl.setHostNode(node);
   }
 });