585806de24
ExoPlayer can be run on a background thread, but some components (UI and IMA) only support players on the main thread. This adds some documentation and assertions for that. To simplify assertions, this also moves the getApplicationLooper method from ExoPlayer to Player. Issue:#4439 ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=213280359