*** Original commit ***
Rollback of https://github.com/google/ExoPlayer/commit/bf5e6c7862ae418895b2b6b26fae9c28aa662ee8
*** Original commit ***
Pass startPositionUs into Renderer.replaceStream
Plumb this down into BaseRenderer.onStreamChanged and use it when
deciding whether to render the first frame of a new period.
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PiperOrigin-RevId: 325218588
