[not for landing] Log loading metrics timestamps.

tracing/tracing/metrics/system_health/loading_metric.html

Index: tracing/tracing/metrics/system_health/loading_metric.html
diff --git a/tracing/tracing/metrics/system_health/loading_metric.html b/tracing/tracing/metrics/system_health/loading_metric.html
index ca12d6f2c42007dad22414994424d9433c3234b0..73ca2f7c457a256bab3e5b97eb979ca979dd94df 100644
--- a/tracing/tracing/metrics/system_health/loading_metric.html
+++ b/tracing/tracing/metrics/system_health/loading_metric.html
@@ -197,7 +197,11 @@ tr.exportTo('tr.metrics.sh', function() {
       var timeToEvent = ev.start - navigationStartEvent.start;
       samples.push({
         value: timeToEvent,
-        diagnostics: {url: new tr.v.d.Generic(url)}
+        diagnostics: {
+          url: new tr.v.d.Generic(url),
+          'Navigation infos': new tr.v.d.Generic(
+              {url: url, pid: rendererHelper.pid, timestamp: ev.start}),
+        }
       });
     }
     return samples;
@@ -225,7 +229,8 @@ tr.exportTo('tr.metrics.sh', function() {
         'End': new RelatedEventSet(fmpMarkerEvent),
         'Navigation infos': new tr.v.d.Generic(
             {url: url, pid: rendererHelper.pid,
-              start: navigationStart.start, fmp: fmpMarkerEvent.start}),
+              start: navigationStart.start, fmp: fmpMarkerEvent.start,
+              timestamp: fmpMarkerEvent.start}),
       }
     });
     return {firstMeaningfulPaint: fmpMarkerEvent.start, url: url};
@@ -274,7 +279,8 @@ tr.exportTo('tr.metrics.sh', function() {
         'Last long task': new RelatedEventSet(lastLongTaskEvent),
         'Navigation infos': new tr.v.d.Generic(
             {url: url, pid: rendererHelper.pid,
-              start: navigationStartTime, interactive: firstInteractive}),
+              start: navigationStartTime, interactive: firstInteractive,
+              timestamp: firstInteractive}),
         'Breakdown of [navStart, Interactive]': breakdownDiagnostic,
       }
     });
@@ -403,6 +409,15 @@ tr.exportTo('tr.metrics.sh', function() {
            firstMeaningfulPaintSamples, firstInteractiveSamples} =
           collectLoadingMetricsForRenderer(rendererHelper);
 
+      console.log('onload timestamps:');
+      console.log(JSON.stringify(firstContentfulPaintSamples.map(x => x.diagnostics['Navigation infos'].value.timestamp)));
+      console.log('first contentful paint timestamps:');
+      console.log(JSON.stringify(firstContentfulPaintSamples.map(x => x.diagnostics['Navigation infos'].value.timestamp)));
+      console.log('first meaningful paint timestamps:');
+      console.log(JSON.stringify(firstMeaningfulPaintSamples.map(x => x.diagnostics['Navigation infos'].value.timestamp)));
+      console.log('first interactive timestamps:');
+      console.log(JSON.stringify(firstInteractiveSamples.map(x => x.diagnostics['Navigation infos'].value.timestamp)));
+
       addSamplesToHistogram(firstContentfulPaintSamples,
           firstContentfulPaintHistogram);
       addSamplesToHistogram(onLoadSamples, onLoadHistogram);