simpleperf: Keep record time and android version in perf.data.

The record time and android version will be shown in html report.
Record time is useful to distinguish reports.
Android version is useful when checking reason for recording results.

Bug: http://b/66914187
Test: run simpleperf_unit_test.
Change-Id: I61ad5df380f8b51a3a6bc1f4dfa4bc9f350a4792
2 files changed