Take 2 at implementing activeTab.

chrome/renderer/extensions/extension_helper.h

Index: chrome/renderer/extensions/extension_helper.h
diff --git a/chrome/renderer/extensions/extension_helper.h b/chrome/renderer/extensions/extension_helper.h
index 4e884679ca3328c9915eb2ee5a447bdf5a14c9d3..99afbde55587f3dca47ab69e5026966c01065d0e 100644
--- a/chrome/renderer/extensions/extension_helper.h
+++ b/chrome/renderer/extensions/extension_helper.h
@@ -59,6 +59,7 @@ class ExtensionHelper
   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_; }
 
@@ -92,6 +93,7 @@ class ExtensionHelper
   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
@@ -129,6 +131,9 @@ class ExtensionHelper
   // 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_;