Take 2 at implementing activeTab.

chrome/browser/extensions/api/offscreen_tabs/offscreen_tabs_api.cc

 // Copyright (c) 2012 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.
 
 #include "chrome/browser/extensions/api/offscreen_tabs/offscreen_tabs_api.h"
 
 #include <algorithm>
 #include <vector>
 
 #include "base/hash_tables.h"
@@ skipping 783 matching lines @@
   OffscreenTab* offscreen_tab = NULL;
   if (!GetMap()->GetOffscreenTab(
           offscreen_tab_id, this, &offscreen_tab, &error_))
     return false;
 
   DictionaryValue* update_props;
   EXTENSION_FUNCTION_VALIDATE(args_->GetDictionary(1, &update_props));
 
   tab_contents_ = offscreen_tab->tab_contents();
   bool is_async = false;
-  if (!UpdateURLIfPresent(update_props, &is_async))
+  if (!UpdateURLIfPresent(update_props, offscreen_tab_id, &is_async))
     return false;
 
   // Update the width and height, if specified.
   if (update_props->HasKey(tabs_keys::kWidthKey) ||
       update_props->HasKey(tabs_keys::kHeightKey)) {
     const gfx::Size& size =
         tab_contents_->web_contents()->GetView()->GetContainerSize();
 
     int width;
     if (update_props->HasKey(tabs_keys::kWidthKey))
@@ skipping 16 matching lines @@
   // async case (when a "javascript": URL is sent to a tab).
   if (!is_async)
     SendResponse(true);
 
   return true;
 }
 
 void UpdateOffscreenTabFunction::PopulateResult() {
   // There's no result associated with this callback.
 }