Track all changed nodes during an update

chrome/common/extensions/api/automation_internal.idl

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // This is the implementation layer of the chrome.automation API, and is
 // essentially a translation of the internal accessibility tree update system
 // into an extension API.
 namespace automationInternal {
   // Data for an accessibility event and/or an atomic change to an accessibility
   // tree. See ui/accessibility/ax_tree_update.h for an extended explanation of
   // the tree update format.
   [nocompile] dictionary AXEventParams {
     // The tree id of the web contents that this update is for.
     long treeID;
 
     // ID of the node that the event applies to.
     long targetID;
 
     // The type of event that this update represents.
     DOMString eventType;
+
+    // The source of this event.
+    DOMString eventFrom;
   };
 
   // All possible actions that can be performed on automation nodes.
   enum ActionType {
     focus,
     doDefault,
     makeVisible,
     setSelection,
     showContextMenu
   };
@@ skipping 69 matching lines @@
     static void onTreeChange(long observerID,
                              long treeID,
                              long nodeID,
                              DOMString changeType);
 
     static void onChildTreeID(long treeID, long nodeID);
 
     static void onNodesRemoved(long treeID, long[] nodeIDs);
   };
 };