[feature] To optimize upload html File object code.

Author: wangxiao

lib/file.js

@@ -334,9 +334,8 @@ module.exports = function(AV) {
       this._source = AV.Promise.as(data.blob, guessedType);
       this._isBlob = true;
     } else if (typeof(File) !== "undefined" && data instanceof File) {
-      this._source = readAsync(data, type);
+      this._source = AV.Promise.as(data, guessedType);
       this._isFileObject = true;
-      this._fileObject = data;
     } else if(AV._isNode && global.Buffer.isBuffer(data)) {
       // use global.Buffer to prevent browserify pack Buffer module
       this._source = AV.Promise.as(data.toString('base64'), guessedType);
@@ -562,7 +561,7 @@ module.exports = function(AV) {
             // TODO: remove this code and use qiniu SDK
             var dataFormat;
             self._previousSave = self._source.then(function(data, type) {
-              dataFormat = self._fileObject || data;
+              dataFormat = data;
               return self._qiniuToken(type);
             }).then(function(response) {
               self._url = response.url;