Implement AutomationNode.querySelector().

extensions/common/extension_messages.h

 // 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.
 
 // IPC messages for extensions.
 // Multiply-included message file, hence no include guard.
 
 #include <string>
 #include <vector>
 
@@ skipping 732 matching lines @@
                      int /* element_instance_id */,
                      int /* guest_instance_id */,
                      base::DictionaryValue /* attach_params */)
 
 // Tells the browser to create a mime handler guest view for a plugin.
 IPC_MESSAGE_CONTROL4(ExtensionHostMsg_CreateMimeHandlerViewGuest,
                      int /* render_frame_id */,
                      std::string /* embedder_url */,
                      std::string /* mime_type */,
                      int /* element_instance_id */)
+
+// Sent when a query selector request is made from the automation API.
+// acc_obj_id is the accessibility tree ID of the starting element.
+IPC_MESSAGE_ROUTED3(ExtensionMsg_AutomationQuerySelector,
+                    int /* request_id */,
+                    int /* acc_obj_id */,
+                    base::string16 /* selector */)
+
+// Result of a query selector request.
+// result_acc_obj_id is the accessibility tree ID of the result element; 0
+// indicates no result.
+IPC_MESSAGE_ROUTED3(ExtensionHostMsg_AutomationQuerySelector_Result,
+                    int /* request_id */,
+                    std::string /* error */,
+                    int /* result_acc_obj_id */)