Do not discard selected tab

chrome/browser/ui/tabs/tab_strip_model.cc

 // 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.
 
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 
 #include <algorithm>
 #include <map>
 #include <string>
 
@@ skipping 187 matching lines @@
   // occurs between the call to add an additional tab and one to close
   // the previous tab.
   InsertTabContentsAt(index + 1, contents, ADD_ACTIVE | ADD_INHERIT_GROUP);
   std::vector<int> closing_tabs;
   closing_tabs.push_back(index);
   InternalCloseTabs(closing_tabs, CLOSE_NONE);
 }
 
 TabContents* TabStripModel::DiscardTabContentsAt(int index) {
   DCHECK(ContainsIndex(index));
+  // Do not discard active tab.
+  if (active_index() == index)
+    return NULL;
+
   TabContents* null_contents = TabContents::Factory::CreateTabContents(
       WebContents::Create(profile(),
                           NULL /* site_instance */,
                           MSG_ROUTING_NONE,
                           NULL /* base_tab_contents */));
   TabContents* old_contents = GetContentsAt(index);
   // Copy over the state from the navigation controller so we preserve the
   // back/forward history and continue to display the correct title/favicon.
   null_contents->web_contents()->GetController().CopyStateFrom(
       old_contents->web_contents()->GetController());
@@ skipping 1097 matching lines @@
 void TabStripModel::ForgetOpenersAndGroupsReferencing(
     const NavigationController* tab) {
   for (TabContentsDataVector::const_iterator i = contents_data_.begin();
        i != contents_data_.end(); ++i) {
     if ((*i)->group == tab)
       (*i)->group = NULL;
     if ((*i)->opener == tab)
       (*i)->opener = NULL;
   }
 }