Cleanup Promise code

src/key.js

@@ -933,7 +933,7 @@ export function readArmored(armoredText) {
  */
 export function generate(options) {
   var packetlist, secretKeyPacket, userIdPacket, dataToSign, signaturePacket, secretSubkeyPacket, subkeySignaturePacket;
-  return new Promise(resolve => resolve()).then(() => {
+  return Promise.resolve().then(() => {
     options.keyType = options.keyType || enums.publicKey.rsa_encrypt_sign;
     if (options.keyType !== enums.publicKey.rsa_encrypt_sign) { // RSA Encrypt-Only and RSA Sign-Only are deprecated and SHOULD NOT be generated
       throw new Error('Only RSA Encrypt or Sign supported');

src/message.js

@@ -92,7 +92,7 @@ Message.prototype.getSigningKeyIds = function() {
  * @return {Message}             new message with decrypted content
  */
 Message.prototype.decrypt = function(privateKey, sessionKey, password) {
-  return new Promise(resolve => resolve()).then(() => {
+  return Promise.resolve().then(() => {
     const keyObj = sessionKey || this.decryptSessionKey(privateKey, password);
     if (!keyObj || !util.isUint8Array(keyObj.data) || !util.isString(keyObj.algorithm)) {
       throw new Error('Invalid session key for decryption.');
@@ -216,7 +216,7 @@ Message.prototype.getText = function() {
  */
 Message.prototype.encrypt = function(keys, passwords) {
   let symAlgo, msg, symEncryptedPacket;
-  return new Promise(resolve => resolve()).then(() => {
+  return Promise.resolve().then(() => {
     if (keys) {
       symAlgo = keyModule.getPreferredSymAlgo(keys);
     } else if (passwords) {

src/openpgp.js

@@ -162,7 +162,7 @@ export function encrypt({ data, publicKeys, privateKeys, passwords, filename, ar
     return asyncProxy.delegate('encrypt', { data, publicKeys, privateKeys, passwords, filename, armor });
   }
 
-  return new Promise(resolve => resolve()).then(() => {
+  return Promise.resolve().then(() => {
 
     let message = createMessage(data, filename);
     if (privateKeys) { // sign the message only if private keys are specified