Amr gives error and chrome closes

[coderpsy]

Synchronous XMLHttpRequest on the main thread is deprecated because of its detrimental effects to the end user's experience. For more help, check https://xhr.spec.whatwg.org/.

xhr.open("GET", chrome.extension.getURL('manifest.json'), false);

AMR extension gives these errors and chrome closes itself in 2 minutes.
i'm using Chrome Canary