A page can't fire dialogs in unload handlers; remove code that handles that case.

content/browser/frame_host/render_frame_host_impl.h

Index: content/browser/frame_host/render_frame_host_impl.h
diff --git a/content/browser/frame_host/render_frame_host_impl.h b/content/browser/frame_host/render_frame_host_impl.h
index d21b1da7281e10bae3131ec5e7820cfbfafaa80e..0e0c532dc8d9891b9b0cc9098c71dda1b7e050cb 100644
--- a/content/browser/frame_host/render_frame_host_impl.h
+++ b/content/browser/frame_host/render_frame_host_impl.h
@@ -879,6 +879,10 @@ class CONTENT_EXPORT RenderFrameHostImpl
   void OnRendererConnect(const service_manager::ServiceInfo& local_info,
                          const service_manager::ServiceInfo& remote_info);
 
+  void SendJavaScriptDialogReply(IPC::Message* reply_msg,
+                                 bool success,
+                                 const base::string16& user_input);
+
   // Returns ownership of the NavigationHandle associated with a navigation that
   // just committed.
   std::unique_ptr<NavigationHandleImpl> TakeNavigationHandleForCommit(