Close the hovered tab on middle mouse click in the Linux tabstrip.

chrome/browser/gtk/tabs/tab_strip_gtk.cc

 // Copyright (c) 2009 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/gtk/tabs/tab_strip_gtk.h"
 
 #include "base/gfx/gtk_util.h"
 #include "base/gfx/point.h"
 #include "chrome/browser/browser.h"
 #include "chrome/browser/gtk/tabs/tab_button_gtk.h"
@@ skipping 1199 matching lines @@
              !tab->closing()) {
     tabstrip->model()->SelectTabContentsAt(tabstrip->hover_index_, true);
   }
 
   return TRUE;
 }
 
 // static
 gboolean TabStripGtk::OnMouseRelease(GtkWidget* widget, GdkEventButton* event,
                                      TabStripGtk* tabstrip) {
-  // TODO(jhawkins): Handle middle click.
-  if (event->button == 2)
-    return TRUE;
-
   gfx::Point point(event->x, event->y);
   if (tabstrip->hover_index_ != -1) {
     tabstrip->GetTabAt(tabstrip->hover_index_)->OnMouseRelease(event);
   } else {
     tabstrip->newtab_button_.get()->OnMouseRelease();
   }
 
   return TRUE;
 }
 
@@ skipping 233 matching lines @@
   return TabStripModel::kNoTab;
 }
 
 int TabStripGtk::NormalizeIndexToAttachedTabStrip(int index) {
   if (index >= model_->count())
     return model_->count() - 1;
   if (index == TabStripModel::kNoTab)
     return 0;
   return index;
 }