Asynchronously loads the given URL as a blob. Returns a promise that will resolve to a Blob once loaded, or reject if the URL failed to load. The data is loaded using XMLHttpRequest, which means that in order to make requests to another origin, the server must have Cross-Origin Resource Sharing (CORS) headers enabled.
||String | Promise.<String>||The URL of the data, or a promise for the URL.|
||Object||optional HTTP headers to send with the requests.|
a promise that will resolve to the requested data when loaded.