Change the telemetry_chrome_hangs pig to also collect late writes.

This is a very reduced version of the other pull request. Given the bug
in com.mozilla.pig.eval.json.JsonMap, we cannot currently write its output,
so this pull request keeps the current setup of writing the original json.
Merge pull request #5 from espindola/lateWritesWithJason

Change the telemetry_chrome_hangs pig to also collect late writes.