Context: We'd like to try to use the ThreadWatcher code to help identify ANRs that happen in native code on Android. 

I tried to get chrome/browser/metrics/thread_watcher.h working on Android by removing all the "#if !defined(OS_ANDROID)"s and tweaking the threshold constants. It seems to run for a short while but then stops. 

What I'd like to be able to do locally: Run a task that posts a sleep to the UI thread for 4 seconds, and have the ThreadWatcher catch this.