Buffer cross frame paint timing updates.

chrome/common/page_load_metrics/test/page_load_metrics_test_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_TEST_PAGE_LOAD_METRICS_TEST_UTIL_H_
+#define CHROME_COMMON_PAGE_LOAD_METRICS_TEST_PAGE_LOAD_METRICS_TEST_UTIL_H_
+
+namespace page_load_metrics {
+namespace mojom {
+class PageLoadTiming;
+}  // namespace mojom
+}  // namespace page_load_metrics
+
+// Helper that fills in any timing fields that page load metrics requires but
+// that are currently missing.
+void PopulateRequiredTimingFields(
+    page_load_metrics::mojom::PageLoadTiming* inout_timing);
+
+#endif  // CHROME_COMMON_PAGE_LOAD_METRICS_TEST_PAGE_LOAD_METRICS_TEST_UTIL_H_