SDK / exoplayer

If an app wants to reconcile its own state with that of a DownloadManager,
it's helpful to know when the DownloadManager has finished restoring any
previously persisted tasks.

Also suppress initial "state changed to paused" listener invocations for
tasks that are immediately started.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=195594881