Unbreak tabs.onRemove extension API in face of fast tab closure

chrome/browser/ui/unload_controller.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/unload_controller.h"
 
 #include "base/logging.h"
 #include "base/message_loop.h"
 #include "chrome/browser/ui/browser.h"
 #include "chrome/browser/ui/browser_tabstrip.h"
@@ skipping 202 matching lines @@
 
   if (is_attempting_to_close_browser_)
     ClearUnloadState(contents);
 }
 
 bool UnloadController::DetachWebContents(content::WebContents* contents) {
   int index = browser_->tab_strip_model()->GetIndexOfWebContents(contents);
   if (index != TabStripModel::kNoTab &&
       contents->NeedToFireBeforeUnload()) {
     tabs_needing_unload_ack_.insert(contents);
+    contents->OnUnloadAboutToDetach();
     browser_->tab_strip_model()->DetachWebContentsAt(index);
     contents->SetDelegate(detached_delegate_.get());
     contents->OnUnloadDetachedStarted();
     return true;
   }
   return false;
 }
 
 void UnloadController::ProcessPendingTabs() {
   if (!is_attempting_to_close_browser_) {
@@ skipping 124 matching lines @@
 }
 
 void UnloadController::PostTaskForProcessPendingTabs() {
   base::MessageLoop::current()->PostTask(
       FROM_HERE,
       base::Bind(&UnloadController::ProcessPendingTabs,
                  weak_factory_.GetWeakPtr()));
 }
 
 }  // namespace chrome