从谷歌下载文件

Question

我正致力于与salesforce集成Google驱动器。目前，当我尝试使用java脚本下载文件时，我正面临文件损坏。我的代码如下

function downloadGDriveFile() {
    var id = '0B3EI0BFOUwSydHZNZXdIZ3lDZzg';
    var downloadUrl = 'https://www.googleapis.com/drive/v2/files/'+ id+'?alt=media';
    var accessToken = MY ACCESS TOKEN;
    var mType = 'image/jpeg';
    var name = 'Internet_of_Things.jpg';

    if (downloadUrl) {
      var xhr = new XMLHttpRequest();
      xhr.open('GET', downloadUrl);
      xhr.setRequestHeader('Authorization', 'Bearer ' + accessToken);
      xhr.onload = function() {
        onDownload(xhr.response);
      };
      xhr.onerror = function() {
        //downloadFile(null);
      };
      xhr.send();
    }

    else {
      alert("Unable to download file.");
    }
  }

  function onDownload(data) {
    var filename = 'Internet_of_Things.jpg';
    var blob = new Blob([data], { type: "image/jpeg" });

        if (typeof window.navigator.msSaveBlob !== 'undefined') {
            // IE workaround for "HTML7007: One or more blob URLs were revoked by closing the blob for which they were created. These URLs will no longer resolve as the data backing the URL has been freed."
            window.navigator.msSaveBlob(blob, filename);
        } else {
            var URL = window.URL || window.webkitURL;
            var downloadUrl = URL.createObjectURL(blob);
            if (filename) {
                // use HTML5 a[download] attribute to specify filename
                var a = document.createElement("a");
                // safari doesn't support this yet
                if (typeof a.download === 'undefined') {
                    window.location = downloadUrl;
                } else {
                    a.href = downloadUrl;
                    a.download = filename;
                    document.body.appendChild(a);
                    a.click();
                }
            } else {
                //window.location = downloadUrl;
            }
            alert(11);
            //URL.revokeObjectURL(downloadUrl);
            setTimeout(function () { URL.revokeObjectURL(downloadUrl); }, 1); // cleanup
        }
}

下载文件时文件已损坏。文件内容如下所示

����JFIF��hExifMM *＆gt; F（1 N Paint.NETv3.5.11��C��C����＆＃34;��

任何人都可以帮助我解决这个问题。我是否需要对来自Google REST API的响应进行编码或解码？