Keep track in the browser of which frames have onunload and onbeforeunload handlers.

ui/views/controls/webview/web_dialog_view.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 "ui/views/controls/webview/web_dialog_view.h"
 
 #include <vector>
 
 #include "base/strings/utf_string_conversions.h"
 #include "content/public/browser/browser_context.h"
@@ skipping 92 matching lines @@
   // If CloseContents() is called before CanClose(), which is called by
   // RenderViewHostImpl::ClosePageIgnoringUnloadEvents, it indicates
   // beforeunload event should not be fired during closing.
   if ((is_attempting_close_dialog_ && before_unload_fired_) ||
       close_contents_called_) {
     is_attempting_close_dialog_ = false;
     before_unload_fired_ = false;
     return true;
   }
 
-  if (!is_attempting_close_dialog_) {
+  if (!is_attempting_close_dialog_ &&
+      web_view_->web_contents()->NeedToFireBeforeUnload()) {
     // Fire beforeunload event when user attempts to close the dialog.
     is_attempting_close_dialog_ = true;
     web_view_->web_contents()->DispatchBeforeUnload();
   }
   return false;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // WebDialogView, views::WidgetDelegate implementation:
 
@@ skipping 236 matching lines @@
   web_contents->SetDelegate(this);
 
   // Set the delegate. This must be done before loading the page. See
   // the comment above WebDialogUI in its header file for why.
   WebDialogUI::SetDelegate(web_contents, this);
 
   web_view_->LoadInitialURL(GetDialogContentURL());
 }
 
 }  // namespace views