Fix cpuTimeMetric

tracing/tracing/metrics/system_health/cpu_time_metric.html

Index: tracing/tracing/metrics/system_health/cpu_time_metric.html
diff --git a/tracing/tracing/metrics/system_health/cpu_time_metric.html b/tracing/tracing/metrics/system_health/cpu_time_metric.html
index b655f1e57ecac9cef672093e14864a98364af761..b28eb8d56991c37bc0e912f7b132ef248c76311f 100644
--- a/tracing/tracing/metrics/system_health/cpu_time_metric.html
+++ b/tracing/tracing/metrics/system_health/cpu_time_metric.html
@@ -36,6 +36,11 @@ tr.exportTo('tr.metrics.sh', function() {
               !rangeOfInterest.intersectsExplicitRangeInclusive(
                   slice.start, slice.end))
             return;
+          if ((typeof slice.cpuDuration !== 'number') ||
+              isNaN(slice.cpuDuration)) {
+            console.error(slice.cpuDuration, slice.title, slice.category);
+            return;
+          }
           threadCpuTime += slice.cpuDuration;
         });
         processCpuTime += threadCpuTime;