Multi-tab: Adding new Notification when tab selection changes.

chrome/browser/tabs/tab_strip_model.h

Index: chrome/browser/tabs/tab_strip_model.h
diff --git a/chrome/browser/tabs/tab_strip_model.h b/chrome/browser/tabs/tab_strip_model.h
index e711b493a90d0bd02f7b1d5a2ee5dd4d66f52313..140ffe2957d075c0303436ea8190816ff40c40f3 100644
--- a/chrome/browser/tabs/tab_strip_model.h
+++ b/chrome/browser/tabs/tab_strip_model.h
@@ -525,6 +525,10 @@ class TabStripModel : public NotificationObserver {
   // the old active index.
   void NotifyActiveTabChanged(int old_active_index);
 
+  // Notifies the observers that the tab selection has changed. |model| is a
+  // snapshot of the selection_model_ before the change.
+  void NotifySelectionChanged(const TabStripSelectionModel& model);
+
   // Returns the number of New Tab tabs in the TabStripModel.
   int GetNewTabCount() const;