autoWatchBatchDelay options is irrelevant in current version of karma

The problem seems to be caused by the use of _.throttle

fabdbae#diff-e8e0621a959fd2639bcc23cd2601f67fR73

replacing _.throttle with _.debounce fixes the issue

this._emitModified = _.debounce(function () {
    self._emitter.emit('file_list_modified', self.files)
}, this._batchInterval)