* time an edit is committed. A snapshot is stale if its sequence number is not equal to its
   * entry's sequence number.
   */
  private var nextSequenceNumber: Long = 0

  private val cleanupQueue = taskRunner.newQueue()
  private val cleanupTask =
    object : Task("$okHttpName Cache") {
      override fun runOnce(): Long {
        synchronized(this@DiskLruCache) {
          if (!initialized || closed) {