Reland: Buffer cross frame paint timing updates.

chrome/common/page_load_metrics/page_load_metrics_util.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 "chrome/common/page_load_metrics/page_load_metrics_util.h"
+
+#include <algorithm>
+
+#include "base/strings/string_util.h"
+#include "net/base/registry_controlled_domains/registry_controlled_domain.h"
+
+namespace page_load_metrics {
+
+base::Optional<std::string> GetGoogleHostnamePrefix(const GURL& url) {
+  const size_t registry_length =
+      net::registry_controlled_domains::GetRegistryLength(
+          url,
+
+          // Do not include unknown registries (registries that don't have any
+          // matches in effective TLD names).
+          net::registry_controlled_domains::EXCLUDE_UNKNOWN_REGISTRIES,
+
+          // Do not include private registries, such as appspot.com. We don't
+          // want to match URLs like www.google.appspot.com.
+          net::registry_controlled_domains::EXCLUDE_PRIVATE_REGISTRIES);
+
+  const base::StringPiece hostname = url.host_piece();
+  if (registry_length == 0 || registry_length == std::string::npos ||
+      registry_length >= hostname.length()) {
+    return base::Optional<std::string>();
+  }
+
+  // Removes the tld and the preceding dot.
+  const base::StringPiece hostname_minus_registry =
+      hostname.substr(0, hostname.length() - (registry_length + 1));
+
+  if (hostname_minus_registry == "google")
+    return std::string("");
+
+  if (!base::EndsWith(hostname_minus_registry, ".google",
+                      base::CompareCase::INSENSITIVE_ASCII)) {
+    return base::Optional<std::string>();
+  }
+
+  return std::string(hostname_minus_registry.substr(
+      0, hostname_minus_registry.length() - strlen(".google")));
+}
+
+bool IsGoogleHostname(const GURL& url) {
+  return GetGoogleHostnamePrefix(url).has_value();
+}
+
+base::Optional<base::TimeDelta> OptionalMin(
+    const base::Optional<base::TimeDelta>& a,
+    const base::Optional<base::TimeDelta>& b) {
+  if (a && !b)
+    return a;
+  if (b && !a)
+    return b;
+  if (!a && !b)
+    return a;  // doesn't matter which
+  return base::Optional<base::TimeDelta>(std::min(a.value(), b.value()));
+}
+
+}  // namespace page_load_metrics