am c4978805: merge from open-source master

Merge commit 'c4978805dc8837570701629a9b8098e80804ad34'

* commit 'c4978805dc8837570701629a9b8098e80804ad34':
  ImageButton example doesn't work. Default state should be at the last.
  Time.parse3339 range checking and proper 'sec-frac' skip