Allow requesting Automation tree by tabId

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 {
   dictionary Rect {
     long left;
@@ skipping 65 matching lines @@
   };
 
   // Returns the process id and routing id of the tab whose accessibility was
   // enabled using enable().
   callback EnableTabCallback = void(long processID, long routingID);
 
   // Callback called when enableDesktop() returns.
   callback EnableDesktopCallback = void();
 
   interface Functions {
-    // Enable automation of the active tab and retrieves its routing id for use
-    // in future updates.
-    static void enableCurrentTab(EnableTabCallback callback);
+    // Enable automation of the tab with the given id, or the active tab if no
+    // tab id is given, and retrieves its process and routing ids for use in
+    // future updates.
+    static void enableTab(optional long tabId, EnableTabCallback callback);
 
     // Enables desktop automation.
     static void enableDesktop(EnableDesktopCallback callback);
 
     // Performs an action on an automation node.
     static void performAction(PerformActionRequiredParams args,
                               object opt_args);
   };
 
   interface Events {
     // Fired when an accessibility event occurs
     static void onAccessibilityEvent(AXEventParams update);
   };
 };