am 7e397842: Reduce memory usage by the MP4 file writer - Don\'t store timestamp for each output sample - Don\'t store timestamp for statistical data collection if the collection of statistical data is not requested

Merge commit '7e397842d53a4242a019daa4b234910273121c30' into gingerbread-plus-aosp

* commit '7e397842d53a4242a019daa4b234910273121c30':
  Reduce memory usage by the MP4 file writer