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

content/browser/renderer_host/render_view_host.cc

Index: content/browser/renderer_host/render_view_host.cc
diff --git a/content/browser/renderer_host/render_view_host.cc b/content/browser/renderer_host/render_view_host.cc
index 1ee71b1c6285e213dfe6ef2151a25eedb49f4dd8..537b8717b09db7b10d4760538bb8c456c0e77596 100644
--- a/content/browser/renderer_host/render_view_host.cc
+++ b/content/browser/renderer_host/render_view_host.cc
@@ -1205,13 +1205,14 @@ void RenderViewHost::OnMsgRunJavaScriptMessage(
     const std::wstring& default_prompt,
     const GURL& frame_url,
     const int flags,
+    const bool unload_handler_being_run,
     IPC::Message* reply_msg) {
   // While a JS message dialog is showing, tabs in the same process shouldn't
   // process input events.
   process()->set_ignore_input_events(true);
   StopHangMonitorTimeout();
   delegate_->RunJavaScriptMessage(message, default_prompt, frame_url, flags,
-                                  reply_msg,
+                                  unload_handler_being_run, reply_msg,
                                   &are_javascript_messages_suppressed_);
 }