feat(node): uploadPart support file stream (#798)

Author: weiyie

lib/browser/managed-upload.js

@@ -283,12 +283,6 @@ proto._createStream = function _createStream(file, start, end) {
   if (isBlob(file) || isFile(file)) {
     return new WebFileReadStream(file.slice(start, end));
   }
-  // else if (is.string(file)) {
-  //   return fs.createReadStream(file, {
-  //     start: start,
-  //     end: end - 1
-  //   });
-  // }
 
   throw new Error('_createStream requires File/Blob.');
 };

lib/managed-upload.js

@@ -253,7 +253,9 @@ WebFileReadStream.prototype._read = function _read(size) {
 };
 
 proto._createStream = function _createStream(file, start, end) {
-  if (isFile(file)) {
+  if (is.readableStream(file)) {
+    return file;
+  } else if (isFile(file)) {
     return new WebFileReadStream(file.slice(start, end));
   } else if (is.string(file)) {
     return fs.createReadStream(file, {