am 4c85f133: Merge change 20869 into donut

Merge commit '4c85f133e10ceaeb2553adb397d4828a7091e7e6'

* commit '4c85f133e10ceaeb2553adb397d4828a7091e7e6':
  If no interpolator is specified for a progress bar in the theme, default to a LinearInterpolator.