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

chrome/browser/prerender/prerender_contents.h

Index: chrome/browser/prerender/prerender_contents.h
diff --git a/chrome/browser/prerender/prerender_contents.h b/chrome/browser/prerender/prerender_contents.h
index 1b45c8f5ef1db0fb5420a925f04d1fc73b63ad5b..18cf97c48755e516b26c4f87146cfbbd60742f6f 100644
--- a/chrome/browser/prerender/prerender_contents.h
+++ b/chrome/browser/prerender/prerender_contents.h
@@ -111,6 +111,7 @@ class PrerenderContents : public RenderViewHostDelegate,
                                     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);
   virtual void Close(RenderViewHost* render_view_host);