While debugging bug 1053946 I found that some events are missing from the log although there were labels referencing them. After some digging I found that those are events with zero SourceEventId. I'm not sure if zero SourceEventId is normal but I had to remove the filtering so those events were properly logged. We should either assign the SourceEventId with correct value or remove the filter from log utilities.

Record tasks even when the source event type is unknown to collect the complete information for analysis. They could always be filtered out in post-processing. Kyle, you reviewed the first task tracer patch series so I guess this is also yours ;)