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

chrome/browser/gtk/tabs/tab_gtk.cc

 // Copyright (c) 2006-2008 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_gtk.h"
 
 #include "chrome/browser/gtk/menu_gtk.h"
 #include "chrome/common/gfx/path.h"
 #include "chrome/common/l10n_util.h"
 #include "chrome/common/resource_bundle.h"
@@ skipping 128 matching lines @@
 bool TabGtk::OnMousePress(const gfx::Point& point) {
   if (close_button_.get()->IsPointInBounds(point))
     return close_button_.get()->OnMousePress();
 
   return false;
 }
 
 void TabGtk::OnMouseRelease(GdkEventButton* event) {
   close_button_.get()->OnMouseRelease();
 
-  if (event->button == 3) {
+  if (event->button == 2) {
+    delegate_->CloseTab(this);
+  } else if (event->button == 3) {
     ShowContextMenu();
   }
 }
 
 bool TabGtk::OnLeaveNotify() {
   bool paint = set_hovering(false);
   paint |= close_button_.get()->OnLeaveNotify();
   return paint;
 }
 
@@ skipping 55 matching lines @@
   if (!menu_controller_.get())
     menu_controller_.reset(new ContextMenuController(this));
 
   menu_controller_->RunMenu();
 }
 
 void TabGtk::ContextMenuClosed() {
   delegate()->StopAllHighlighting();
   menu_controller_.reset();
 }