Added UkmPageLoadMetricsObserver which sends top-level metrics to UKM

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.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_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_UKM_PAGE_LOAD_METRICS_OBSERVER_H_
+#define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_UKM_PAGE_LOAD_METRICS_OBSERVER_H_
+
+#include "base/macros.h"
+#include "chrome/browser/page_load_metrics/page_load_metrics_observer.h"
+
+// If URL-Keyed-Metrics (UKM) is enabled in the system, this is used to
+// populate it with top-level page-load metrics.
+class UkmPageLoadMetricsObserver
+    : public page_load_metrics::PageLoadMetricsObserver {
+ public:
+  // Returns a UkmPageLoadMetricsObserver, or nullptr if it is not needed.
+  static std::unique_ptr<page_load_metrics::PageLoadMetricsObserver>
+  CreateIfNeeded();
+
+  UkmPageLoadMetricsObserver();
+
+  // page_load_metrics::PageLoadMetricsObserver implementation:
+  ObservePolicy OnStart(content::NavigationHandle* navigation_handle,
+                        const GURL& currently_committed_url,
+                        bool started_in_foreground) override;
+
+  ObservePolicy FlushMetricsOnAppEnterBackground(
+      const page_load_metrics::PageLoadTiming& timing,
+      const page_load_metrics::PageLoadExtraInfo& info) override;
+
+  ObservePolicy OnHidden(
+      const page_load_metrics::PageLoadTiming& timing,
+      const page_load_metrics::PageLoadExtraInfo& info) override;
+
+  void OnComplete(const page_load_metrics::PageLoadTiming& timing,
+                  const page_load_metrics::PageLoadExtraInfo& info) override;
+
+ private:
+  void SendMetricsToUkm(const page_load_metrics::PageLoadTiming& timing,
+                        const page_load_metrics::PageLoadExtraInfo& info);
+
+  DISALLOW_COPY_AND_ASSIGN(UkmPageLoadMetricsObserver);
+};
+
+#endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_UKM_PAGE_LOAD_METRICS_OBSERVER_H_