Changes instant so that the newly created tab has a new id. Doing

chrome/browser/tabs/tab_strip_model_observer.h

 // Copyright (c) 2010 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_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 #define CHROME_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_
 #pragma once
 
 class TabContentsWrapper;
 class TabStripModel;
@@ skipping 67 matching lines @@
   // The specified TabContents at |index| changed in some way. |contents| may
   // be an entirely different object and the old value is no longer available
   // by the time this message is delivered.
   //
   // See TabChangeType for a description of |change_type|.
   virtual void TabChangedAt(TabContentsWrapper* contents,
                             int index,
                             TabChangeType change_type);
 
   // The tab contents was replaced at the specified index. This is invoked when
-  // a tab becomes phantom. See description of phantom tabs in class description
-  // of TabStripModel for details.
-  virtual void TabReplacedAt(TabContentsWrapper* old_contents,
+  // instant is enabled and the user navigates by way of instant.
+  virtual void TabReplacedAt(TabStripModel* tab_strip_model,
+                             TabContentsWrapper* old_contents,
                              TabContentsWrapper* new_contents,
                              int index);
 
   // Invoked when the pinned state of a tab changes. See note in
   // TabMiniStateChanged as to how this relates to TabMiniStateChanged.
   virtual void TabPinnedStateChanged(TabContentsWrapper* contents, int index);
 
   // Invoked if the mini state of a tab changes.
   // NOTE: this is sent when the pinned state of a non-app tab changes and is
   // sent in addition to TabPinnedStateChanged. UI code typically need not care
@@ skipping 12 matching lines @@
 
   // Sent when the tabstrip model is about to be deleted and any reference held
   // must be dropped.
   virtual void TabStripModelDeleted();
 
  protected:
   virtual ~TabStripModelObserver() {}
 };
 
 #endif  // CHROME_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_