Speculative bug fixes

- change setBackground to setBackgroundDrawable for compatibility.
- Possible place for ClassCastException. root is from onKey, but
  all possible paths from onKey is type-checked before cast, so
  this is the only location I can see that might throw exception.

b/17549422

Change-Id: I3e3a7528c689f03704d53b7359bc2024770effd3
2 files changed