Buffer cross frame paint timing updates.

chrome/common/page_load_metrics/page_load_metrics_util.h

+// 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.
+
+#ifndef CHROME_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UTIL_H_
+#define CHROME_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UTIL_H_
+
+#include <string>
+
+#include "base/optional.h"
+#include "base/time/time.h"
+#include "url/gurl.h"
+
+namespace page_load_metrics {
+
+// Returns the minimum value of the optional TimeDeltas, if both values are
+// set. Otherwise, if one value is set, returns that value. Otherwise, returns
+// an unset value.
+base::Optional<base::TimeDelta> OptionalMin(
+    const base::Optional<base::TimeDelta>& a,
+    const base::Optional<base::TimeDelta>& b);
+
+// Whether the given url has a google hostname.
+bool IsGoogleHostname(const GURL& url);
+
+// If the given hostname is a google hostname, returns the portion of the
+// hostname before the google hostname. Otherwise, returns an unset optional
+// value.
+//
+// For example:
+//   https://example.com/foo => returns an unset optional value
+//   https://google.com/foo => returns ''
+//   https://www.google.com/foo => returns 'www'
+//   https://news.google.com/foo => returns 'news'
+//   https://a.b.c.google.com/foo => returns 'a.b.c'
+base::Optional<std::string> GetGoogleHostnamePrefix(const GURL& url);
+
+}  // namespace page_load_metrics
+
+#endif  // CHROME_COMMON_PAGE_LOAD_METRICS_PAGE_LOAD_METRICS_UTIL_H_