static reviver_(key, value) {
    if (value && value.__type__ == 'ArrayBuffer') {
      return shaka.util.BufferUtils.toArrayBuffer(
          shaka.util.Uint8ArrayUtils.fromBase64(value.__value__));
    }
    return value;
  }
A reviver callback for JSON.parse.  It recognizes special objects from
replacer_ and turns them back into their original format.

@param {string} key
@param {?} value
@return {?}
@private