Multi-tab: Adding new Notification when tab selection changes (again).

chrome/browser/tabs/tab_strip_model_observer.h

Index: chrome/browser/tabs/tab_strip_model_observer.h
diff --git a/chrome/browser/tabs/tab_strip_model_observer.h b/chrome/browser/tabs/tab_strip_model_observer.h
index b2753508c3a3b43e9da450429fcab804dad735de..5a69eb55b187234ce6d333d19b39e3966599ba2a 100644
--- a/chrome/browser/tabs/tab_strip_model_observer.h
+++ b/chrome/browser/tabs/tab_strip_model_observer.h
@@ -8,6 +8,7 @@
 
 class TabContentsWrapper;
 class TabStripModel;
+class TabStripSelectionModel;
 
 ////////////////////////////////////////////////////////////////////////////////
 //
@@ -61,24 +62,26 @@ class TabStripModelObserver {
   // happens.
   virtual void TabDeactivated(TabContentsWrapper* contents);
 
-  // Sent when the selection changes. The previously selected tab is identified
-  // by |old_contents| and the newly selected tab by |new_contents|. |index| is
-  // the index of |new_contents|. When using multiple selection this may be sent
-  // even when the active tab has not changed. For example, if the selection is
-  // extended this method is invoked to inform observers the selection has
-  // changed, but |old_contents| and |new_contents| are the same.  If you only
-  // care about when the active tab changes, check for when |old_contents|
-  // differs from |new_contents|. |user_gesture| specifies whether or not this
+  // Sent when the active tab changes. The previously active tab is identified
+  // by |old_contents| and the newly active tab by |new_contents|. |index| is
+  // the index of |new_contents|. |user_gesture| specifies whether or not this
   // was done by a user input event (e.g. clicking on a tab, keystroke) or as a
   // side-effect of some other function.
-  //
-  // TODO(dpapad): Add TabSelectionChanged method for when the selected tabs
-  // change.
+  // Note: It is possible for the selection to change while the active tab
+  // remains unchanged. For example, control-click may not change the active tab
+  // but does change the selection. In this case |ActiveTabChanged| is not sent.
+  // If you care about any changes to the selection, override
+  // TabSelectionChanged.
   virtual void ActiveTabChanged(TabContentsWrapper* old_contents,
                                 TabContentsWrapper* new_contents,
                                 int index,
                                 bool user_gesture);
 
+  // Sent when the selection changes. More precisely when selected tabs, anchor
+  // tab or active tab change. |old_model| is a snapshot of the selection model
+  // before the change. See also ActiveTabChanged for details.
+  virtual void TabSelectionChanged(const TabStripSelectionModel& old_model);
+
   // The specified TabContents at |from_index| was moved to |to_index|.
   virtual void TabMoved(TabContentsWrapper* contents,
                         int from_index,