SDK / exoplayer

- This change marks the methods that will be removed, and
  renames the Window methods to remove "Window" from their
  names.
- The Window methods need to be made to work (rather than
  throw exceptions) when the timeline isn't set. Once that
  gets done in a subsequent CL, the deprecated methods will
  be removed.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=130612979