firstPaintMetric: Report timeToOnload metric to check PCv1/v2 consistency

tracing/tracing/metrics/system_health/first_paint_metric.html

Index: tracing/tracing/metrics/system_health/first_paint_metric.html
diff --git a/tracing/tracing/metrics/system_health/first_paint_metric.html b/tracing/tracing/metrics/system_health/first_paint_metric.html
index 3d12cf915f50f0ec38114d7b06bb20dd09a4fd72..8740ef0b358a54b736a6803c9b8d3ef034e6d9cf 100644
--- a/tracing/tracing/metrics/system_health/first_paint_metric.html
+++ b/tracing/tracing/metrics/system_health/first_paint_metric.html
@@ -74,8 +74,8 @@ tr.exportTo('tr.metrics.sh', function() {
     }
   }
 
-  function findUrlOfFrameAt(rendererHelper, frameIdRef, ts) {
-    var url;
+  function findFrameLoaderSnapshotAt(rendererHelper, frameIdRef, ts) {
+    var snapshot;
 
     var objects = rendererHelper.process.objects;
     var frameLoaderInstances = objects.instancesByTypeName_['FrameLoader'];
@@ -88,18 +88,18 @@ tr.exportTo('tr.metrics.sh', function() {
     frameLoaderInstances.forEach(function(instance) {
       if (!instance.isAliveAt(ts))
         return;
-      var snapshot = instance.getSnapshotAt(ts);
-      if (frameIdRef !== snapshot.args['frame']['id_ref'])
+      var maybeSnapshot = instance.getSnapshotAt(ts);
+      if (frameIdRef !== maybeSnapshot.args['frame']['id_ref'])
         return;
 
-      url = snapshot.args['documentLoaderURL'];
+      snapshot = maybeSnapshot;
     }, this);
 
-    return url;
+    return snapshot;
   }
 
-  function findFirstPaintEvents(rendererHelper, title) {
-    var firstPaintEvents = [];
+  function findAllUserTimingEvents(rendererHelper, title) {
+    var targetEvents = [];
 
     rendererHelper.process.iterateAllEvents(
         function(ev) {
@@ -107,10 +107,10 @@ tr.exportTo('tr.metrics.sh', function() {
               ev.title !== title)
             return;
 
-          firstPaintEvents.push(ev);
+          targetEvents.push(ev);
         }, this);
 
-    return firstPaintEvents;
+    return targetEvents;
   }
 
   function prepareTelemetryInternalEventPredicate(rendererHelper) {
@@ -142,6 +142,19 @@ tr.exportTo('tr.metrics.sh', function() {
     return URL_BLACKLIST.indexOf(url) >= 0;
   }
 
+  var METRICS = [
+    {
+      valueName: 'firstContentfulPaint',
+      title: 'firstContentfulPaint',
+      description: 'time to first contentful paint'
+    },
+    {
+      valueName: 'timeToOnload',
+      title: 'loadEventStart',
+      description: 'time to onload. ' +
+        'This is temporary metric used for PCv1/v2 sanity checking'
+    }];
+
   function firstPaintMetric(values, model) {
     var chromeHelper = model.getOrCreateHelper(
         tr.model.helpers.ChromeModelHelper);
@@ -151,41 +164,45 @@ tr.exportTo('tr.metrics.sh', function() {
     var findNavigationStartEventForFrameBeforeTimestamp =
         navigationStartFinder(rendererHelper);
 
-    var numericBuilder =
-      new tr.v.NumericBuilder(timeDurationInMs_smallerIsBetter, 0)
-      .addLinearBins(1000, 20) // 50ms step to 1s
-      .addLinearBins(3000, 20) // 100ms step to 3s
-      .addExponentialBins(20000, 20);
-    var firstContentfulPaintHistogram = numericBuilder.build();
-    firstContentfulPaintHistogram.customizeSummaryOptions({
-      avg: true,
-      count: true,
-      max: true,
-      min: true,
-      std: true,
-      sum: false,
-      percentile: [0.90, 0.95, 0.99],
-    });
-
-    var firstPaintEvents = findFirstPaintEvents(rendererHelper,
-        'firstContentfulPaint');
-    firstPaintEvents = firstPaintEvents.filter(
-        (ev) => !isTelemetryInternalEvent(ev));
-    firstPaintEvents.forEach(function(ev) {
-      var frameIdRef = ev.args['frame'];
-      var url = findUrlOfFrameAt(rendererHelper, frameIdRef, ev.start);
-      if (url === undefined || shouldIgnoreURL(url))
-        return;
-      var navigationStartEvent =
-        findNavigationStartEventForFrameBeforeTimestamp(frameIdRef, ev.start);
+    METRICS.forEach(function(metric) {
+      var numericBuilder =
+        new tr.v.NumericBuilder(timeDurationInMs_smallerIsBetter, 0)
+        .addLinearBins(1000, 20) // 50ms step to 1s
+        .addLinearBins(3000, 20) // 100ms step to 3s
+        .addExponentialBins(20000, 20);
+      var histogram = numericBuilder.build();
+      histogram.customizeSummaryOptions({
+        avg: true,
+        count: false,
+        max: true,
+        min: true,
+        std: true,
+        sum: false,
+        percentile: [0.90, 0.95, 0.99],
+      });
+
+      var targetEvents = findAllUserTimingEvents(rendererHelper, metric.title);
+      targetEvents = targetEvents.filter(
+          (ev) => !isTelemetryInternalEvent(ev));
+      targetEvents.forEach(function(ev) {
+        var frameIdRef = ev.args['frame'];
+        var snapshot =
+          findFrameLoaderSnapshotAt(rendererHelper, frameIdRef, ev.start);
+        if (snapshot === undefined || !snapshot.args.isLoadingMainFrame)
+          return;
+        var url = snapshot.args.documentLoaderURL;
+        if (shouldIgnoreURL(url))
+          return;
+        var navigationStartEvent =
+          findNavigationStartEventForFrameBeforeTimestamp(frameIdRef, ev.start);
 
-      var timeToFirstContentfulPaint = ev.start - navigationStartEvent.start;
-      firstContentfulPaintHistogram.add(timeToFirstContentfulPaint, {url: url});
+        var timeToEvent = ev.start - navigationStartEvent.start;
+        histogram.add(timeToEvent, {url: url});
+      }, this);
+      values.addValue(new tr.v.NumericValue(
+          model.canonicalUrl, metric.valueName, histogram,
+          { description: metric.description }));
     }, this);
-    values.addValue(new tr.v.NumericValue(
-        model.canonicalUrl, 'firstContentfulPaint',
-        firstContentfulPaintHistogram,
-        { description: 'time to first contentful paint' }));
   }
 
   firstPaintMetric.prototype = {