background.js

function sendFile() {
  var x = new XMLHttpRequest();
  x.open("GET", blobURL);
  x.responseType = "blob";
  x.onload = function () {
    var url = URL.createObjectURL(x.response);
    localStorage.setItem("fileToProcess", url);
    window.onload = function () {
      document.getElementById("fetchImageFromBlob").click();
    };
  };
  x.send();
}