SDK / exoplayer

(Fixing GitHub issue #2699)

Added controllerAutoShow parameter to decide whether playback controls are
shown automatically. Default is true. Can be overwritten in the XML with
auto_show=false or via SimpleExoPlayerView.setControllerAutoShow(false).

Also inverted the logic of maybeShowControllers and showController.
SimpleExoPlayerView.(show/hide)Controller and PlaybackControlView.(show/hide)
now unconditionally do what they say to allow manual operation.
SimpleExoPlayerView.maybeShowController is used internally to automatically
show playback controls.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=158712277