Ignore JavaScript messages (alert/confirm/prompt) during unload handlers.

content/browser/tab_contents/tab_contents.cc

 // Copyright (c) 2011 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 "content/browser/tab_contents/tab_contents.h"
 
 #include <cmath>
 
 #include "base/auto_reset.h"
 #include "base/metrics/histogram.h"
@@ skipping 2407 matching lines @@
                                              const std::string& target) {
   if (delegate())
     delegate()->ForwardMessageToExternalHost(message, origin, target);
 }
 
 void TabContents::RunJavaScriptMessage(
     const std::wstring& message,
     const std::wstring& default_prompt,
     const GURL& frame_url,
     const int flags,
+    const bool unload_handler_being_run,
     IPC::Message* reply_msg,
     bool* did_suppress_message) {
   // Suppress javascript messages when requested and when inside a constrained
   // popup window (because that activates them and breaks them out of the
   // constrained window jail).
   // Also suppress messages when showing an interstitial. The interstitial is
   // shown over the previous page, we don't want the hidden page dialogs to
   // interfere with the interstitial.
+  // Also suppress messages during beforeunload/unload event handlers.
   bool suppress_this_message =
       suppress_javascript_messages_ ||
       showing_interstitial_page() ||
+      unload_handler_being_run ||
       (delegate() && delegate()->ShouldSuppressDialogs());
   if (delegate())
     suppress_this_message |=
         (delegate()->GetConstrainingContents(this) != this);
 
   *did_suppress_message = suppress_this_message;
 
   if (!suppress_this_message) {
     base::TimeDelta time_since_last_message(
         base::TimeTicks::Now() - last_javascript_message_dismissal_);
@@ skipping 405 matching lines @@
 }
 
 bool TabContents::MaybeUsePreloadedPage(const GURL& url) {
   prerender::PrerenderManager* pm = profile()->GetPrerenderManager();
   if (pm != NULL) {
     if (pm->MaybeUsePreloadedPage(this, url))
       return true;
   }
   return false;
 }