Race condition for _tick and _reported

[tovchenko]

1. Let assume that we use all the default callbacks and values.
2. When the _ticker is not called during 5sec and we recognise this as ANR and send the report, assign interval initial value and set the _reported to true.
3. We start our while cycle from the beginning: _tick is not 0 so we don't schedule _ticker again - it is ok, next we put our thread to the sleep on 5sec one more time.
4. But imagine that our _ticker is not called again during this 5s but is called at the time when we step on condition "if (_tick != 0 && !_reported)" and it is race condition because we write and read _tick and _reported at the same moment of time.

Best,
Taras