Take 2 at implementing activeTab.

chrome/renderer/extensions/extension_helper.h

 // 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.
 
 #ifndef CHROME_RENDERER_EXTENSIONS_EXTENSION_HELPER_H_
 #define CHROME_RENDERER_EXTENSIONS_EXTENSION_HELPER_H_
 #pragma once
 
 #include <map>
 #include <vector>
@@ skipping 41 matching lines @@
                   ExtensionDispatcher* extension_dispatcher);
   virtual ~ExtensionHelper();
 
   // Starts installation of the page in the specified frame as a web app. The
   // page must link to an external 'definition file'. This is different from
   // the 'application shortcuts' feature where we pull the application
   // definition out of optional meta tags in the page.
   bool InstallWebApplicationUsingDefinitionFile(WebKit::WebFrame* frame,
                                                 string16* error);
 
+  int tab_id() const { return tab_id_; }
   int browser_window_id() const { return browser_window_id_; }
   chrome::ViewType view_type() const { return view_type_; }
 
  private:
   // RenderViewObserver implementation.
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
   virtual void DidFinishDocumentLoad(WebKit::WebFrame* frame) OVERRIDE;
   virtual void DidFinishLoad(WebKit::WebFrame* frame) OVERRIDE;
   virtual void DidCreateDocumentElement(WebKit::WebFrame* frame) OVERRIDE;
   virtual void DidStartProvisionalLoad(WebKit::WebFrame* frame) OVERRIDE;
@@ skipping 13 matching lines @@
                                     const std::string& channel_name,
                                     const std::string& tab_json,
                                     const std::string& source_extension_id,
                                     const std::string& target_extension_id);
   void OnExtensionDeliverMessage(int target_port_id,
                                  const std::string& message);
   void OnExtensionDispatchOnDisconnect(int port_id, bool connection_error);
   void OnExecuteCode(const ExtensionMsg_ExecuteCode_Params& params);
   void OnGetApplicationInfo(int page_id);
   void OnNotifyRendererViewType(chrome::ViewType view_type);
+  void OnSetTabId(int tab_id);
   void OnUpdateBrowserWindowId(int window_id);
 
   // Callback triggered when we finish downloading the application definition
   // file.
   void DidDownloadApplicationDefinition(const WebKit::WebURLResponse& response,
                                         const std::string& data);
 
   // Callback triggered after each icon referenced by the application definition
   // is downloaded.
   void DidDownloadApplicationIcon(webkit_glue::ImageResourceFetcher* fetcher,
@@ skipping 17 matching lines @@
       ImageResourceFetcherList;
   ImageResourceFetcherList app_icon_fetchers_;
 
   // The number of app icon requests outstanding. When this reaches zero, we're
   // done processing an app definition file.
   int pending_app_icon_requests_;
 
   // Type of view attached with RenderView.
   chrome::ViewType view_type_;
 
+  // Id of the tab which the RenderView is attached to.
+  int tab_id_;
+
   // Id number of browser window which RenderView is attached to.
   int browser_window_id_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionHelper);
 };
 
 #endif  // CHROME_RENDERER_EXTENSIONS_EXTENSION_HELPER_H_