Sync XHR should hang the page while waiting for the response. It should not hang the whole browser, but it should pause rendering and event processing on the pa

Sync XHR should hang the page while waiting for the response. It should not hang the whole browser, but it should pause rendering and event processing on the page - i.e. cause the page to be unresponsive. Otherwise it wouldn't be synchronous. A different issue is whether the synchronous mode of XHR was a good idea in the first place. But what's done is done.