Reland fast tab closure behind a flag

chrome/browser/ui/gtk/browser_window_gtk.cc

 // Copyright 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/gtk/browser_window_gtk.h"
 
 #include <gdk/gdkkeysyms.h>
 
 #include <algorithm>
 #include <string>
@@ skipping 1425 matching lines @@
   // You cannot close a frame for which there is an active originating drag
   // session.
   if (tabstrip_->IsDragSessionActive())
     return false;
 
   // Give beforeunload handlers the chance to cancel the close before we hide
   // the window below.
   if (!browser_->ShouldCloseWindow())
     return false;
 
+  bool fast_tab_closing_enabled =
+      CommandLine::ForCurrentProcess()->HasSwitch(switches::kEnableFastUnload);
+
   if (!browser_->tab_strip_model()->empty()) {
     // Tab strip isn't empty.  Hide the window (so it appears to have closed
     // immediately) and close all the tabs, allowing the renderers to shut
     // down. When the tab strip is empty we'll be called back again.
     gtk_widget_hide(GTK_WIDGET(window_));
     browser_->OnWindowClosing();
+
+    if (fast_tab_closing_enabled)
+      browser_->tab_strip_model()->CloseAllTabs();
+    return false;
+  } else if (fast_tab_closing_enabled &&
+      !browser_->HasCompletedUnloadProcessing()) {
+    // The browser needs to finish running unload handlers.
+    // Hide the window (so it appears to have closed immediately), and
+    // the browser will call us back again when it is ready to close.
+    gtk_widget_hide(GTK_WIDGET(window_));
     return false;
   }
 
   // Empty TabStripModel, it's now safe to allow the Window to be closed.
   content::NotificationService::current()->Notify(
       chrome::NOTIFICATION_WINDOW_CLOSED,
       content::Source<GtkWindow>(window_),
       content::NotificationService::NoDetails());
   return true;
 }
@@ skipping 942 matching lines @@
           wm_type == ui::WM_OPENBOX ||
           wm_type == ui::WM_XFWM4);
 }
 
 // static
 BrowserWindow* BrowserWindow::CreateBrowserWindow(Browser* browser) {
   BrowserWindowGtk* browser_window_gtk = new BrowserWindowGtk(browser);
   browser_window_gtk->Init();
   return browser_window_gtk;
 }