Fix the Contention Stacks view for .NET Framework and older .NET Core (…

…#2038)

processes.

This change will use the time difference between the Contention/Start
and Contention/Stop event unless the process is running on a newer
version of .NET Core that specifies the time difference in the
Contention/Stop event.  This is the ensure that this view works for all
.NET processes and not just newer .NET Core processes.

src/TraceEvent/Computers/StartStopLatencyComputer.cs

@@ -38,7 +38,10 @@ protected override void RecordAdditionalDataOnStartWithoutStop(StackSourceSample
         protected override void RecordAdditionalStopData(StackSourceSample sample, TraceEvent data)
         {
             var stopData = (ContentionStopTraceData) data;
-            sample.Metric = (float) (stopData.DurationNs / NanosInMillisecond);
+            if (stopData.DurationNs > 0)
+            {
+                sample.Metric = (float)(stopData.DurationNs / NanosInMillisecond);
+            }
             sample.StackIndex = _interner.CallStackIntern(_interner.FrameIntern($"EventData DurationNs {stopData.DurationNs:N0}"), sample.StackIndex);
         }
     }