metrics: Display Some of Web Vital Metrics in HUD

This CL starts display actual web vital metrics in the HUD overlay.

This CL creates a WebVitalMetrics data structure, and hooks up its
source from Blink to display in cc.

This CL also initialize the actual value for largest contentful load
and first input delay in the WebVitalMetrics class.

R=sadrul

Bug: 1149385
Change-Id: I8d89dd5a689c52abb8f400a484f0a9087edd3a77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2541806
Commit-Queue: weiliangc <weiliangc@chromium.org>
Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Reviewed-by: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829827}

diff --git a/cc/metrics/web_vital_metrics.cc b/cc/metrics/web_vital_metrics.cc
new file mode 100644
index 0000000..d27f6b3
--- /dev/null
+++ b/cc/metrics/web_vital_metrics.cc

@@ -0,0 +1,23 @@
+// Copyright 2020 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 "cc/metrics/web_vital_metrics.h"
+
+namespace cc {
+
+WebVitalMetrics::WebVitalMetrics() = default;
+
+WebVitalMetrics::WebVitalMetrics(const WebVitalMetrics& other) = default;
+
+bool WebVitalMetrics::HasValue() const {
+  if (largest_contentful_paint.has_value())
+    return true;
+
+  if (first_input_delay.has_value())
+    return true;
+
+  return false;
+}
+
+}  // namespace cc