Add support for logging additional metrics in UKM.

components/ukm/ukm_source.cc

 // Copyright 2017 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/ukm/ukm_source.h"
 #include "components/metrics/proto/ukm/source.pb.h"
 
 namespace ukm {
 
 UkmSource::UkmSource() = default;
 
 UkmSource::~UkmSource() = default;
 
 void UkmSource::PopulateProto(Source* proto_source) {
-  proto_source->set_url(committed_url_.spec());
+  proto_source->set_url(url_.spec());
 
-  proto_source->set_first_contentful_paint_msec(
-      first_contentful_paint_.InMilliseconds());
+  if (parse_start_)
+    proto_source->set_parse_start_msec(parse_start_.value().InMilliseconds());
+  if (total_time_)
+    proto_source->set_total_time_msec(total_time_.value().InMilliseconds());
+
+  if (first_contentful_paint_) {
+    proto_source->set_first_contentful_paint_msec(
+        first_contentful_paint_.value().InMilliseconds());
+  }
+  if (first_meaningful_paint_) {
+    proto_source->set_experimental_first_meaningful_paint_msec(
+        first_meaningful_paint_.value().InMilliseconds());
+  }
 }
 
 }  // namespace ukm