miguely 4ef1f94011 Backlayer: Keep the value of expanded across activity restarts and config changes using onSaveInstanceState and onRestoreInstanceState.
This CL also changes the API from a explicit expand()/collapse() method duo to a single setExpanded(boolean) to match other expandable widgets in MDC, for consistency.

This is a breaking change but there has been no release of MDC that contains BackLayerLayout in a usable state, so this is the right time to do this kind of change.

PiperOrigin-RevId: 164664813
2017-09-21 14:22:28 -04:00
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