          type: Object,
          value: null,
          observer: '_taskChanged'
        },

        /**
        *  Number of bytes transferred
        */
        bytesTransferred: {
          type: Number,
          notify: true
        },

        /**
        *  Total number of bytes of the file
        */
        totalBytes: {
          type: Number,
          notify: true
        },

        /**
        *  The upload task's state
        */
        state: {
          type: Object,
          notify: tru