Adding UMA on page load size for pages with Media

chrome/browser/page_load_metrics/observers/media_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_MEDIA_PAGE_LOAD_METRICS_OBSERVER_H_
+#define CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_MEDIA_PAGE_LOAD_METRICS_OBSERVER_H_
+
+#include <stdint.h>
+
+#include "base/macros.h"
+#include "chrome/browser/page_load_metrics/page_load_metrics_observer.h"
+
+namespace page_load_metrics {
+struct PageLoadExtraInfo;
+struct PageLoadTiming;
+}
+
+// Observer responsible for recording metrics on pages that load at least one
+// MEDIA request.
+class MediaPageLoadMetricsObserver
+    : public page_load_metrics::PageLoadMetricsObserver {
+ public:
+  MediaPageLoadMetricsObserver();
+  ~MediaPageLoadMetricsObserver() override;
+
+  // page_load_metrics::PageLoadMetricsObserver:
+  void OnComplete(const page_load_metrics::PageLoadTiming& timing,
+                  const page_load_metrics::PageLoadExtraInfo& info) override;
+  page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+  FlushMetricsOnAppEnterBackground(
+      const page_load_metrics::PageLoadTiming& timing,
+      const page_load_metrics::PageLoadExtraInfo& info) override;
+  void OnLoadedResource(
+      const page_load_metrics::ExtraRequestInfo& extra_request_info) override;
+  void OnLoadingBehaviorObserved(
+      const page_load_metrics::PageLoadExtraInfo& info) override;
+
+ private:
+  // Records histograms for byte information.
+  void RecordByteHistograms();
+
+  // Whether the page load played a media element.
+  bool played_media_;

[Charlie Harrison, 2017/03/08 14:33:58]

nit: can you put the bool at the end to avoid padding?

[RyanSturm, 2017/03/08 17:45:36]

Done.

+
+  // The number of body (not header) prefilter bytes consumed by requests for
+  // the page.
+  int64_t cache_bytes_;
+  int64_t network_bytes_;
+
+  DISALLOW_COPY_AND_ASSIGN(MediaPageLoadMetricsObserver);
+};
+
+#endif  // CHROME_BROWSER_PAGE_LOAD_METRICS_OBSERVERS_MEDIA_PAGE_LOAD_METRICS_OBSERVER_H_