Adding UMA on page load size for pages with Media

chrome/browser/page_load_metrics/observers/media_page_load_metrics_observer.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/browser/page_load_metrics/observers/media_page_load_metrics_observer.h"
+
+#include "chrome/browser/page_load_metrics/page_load_metrics_util.h"
+#include "chrome/common/page_load_metrics/page_load_timing.h"
+#include "third_party/WebKit/public/platform/WebLoadingBehaviorFlag.h"
+
+namespace {
+
+const char kHistogramNetworkBytes[] =
+    "PageLoad.Clients.MediaPageLoad.Experimental.Bytes.Network";
+const char kHistogramCacheBytes[] =
+    "PageLoad.Clients.MediaPageLoad.Experimental.Bytes.Cache";
+const char kHistogramTotalBytes[] =
+    "PageLoad.Clients.MediaPageLoad.Experimental.Bytes.Total";
+
+}  // namespace
+
+MediaPageLoadMetricsObserver::MediaPageLoadMetricsObserver()
+    : played_media_(false), cache_bytes_(0), network_bytes_(0) {}
+
+MediaPageLoadMetricsObserver::~MediaPageLoadMetricsObserver() {}
+
+void MediaPageLoadMetricsObserver::OnLoadedResource(
+    const page_load_metrics::ExtraRequestInfo& extra_request_info) {
+  if (extra_request_info.was_cached) {
+    cache_bytes_ += extra_request_info.raw_body_bytes;
+  } else {
+    network_bytes_ += extra_request_info.raw_body_bytes;
+  }
+}
+
+page_load_metrics::PageLoadMetricsObserver::ObservePolicy
+MediaPageLoadMetricsObserver::FlushMetricsOnAppEnterBackground(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  if (!played_media_)
+    return STOP_OBSERVING;
+  // FlushMetricsOnAppEnterBackground is invoked on Android in cases where the
+  // app is about to be backgrounded, as part of the Activity.onPause()
+  // flow. After this method is invoked, Chrome may be killed without further
+  // notification, so we record final metrics collected up to this point.
+  if (!info.did_commit) {
+    RecordByteHistograms();

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

Don't we want to Record only if the page commit?

Optional:
I think it would simplify the flow if this method was rewritten:

if (played_media_ && info.did_commit)
  RecordByteHistograms()
return STOP_OBSERVING;

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

Wow. Thanks for finding that. Added a test case.

+  }
+  return STOP_OBSERVING;
+}
+
+void MediaPageLoadMetricsObserver::OnComplete(
+    const page_load_metrics::PageLoadTiming& timing,
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  if (!played_media_)
+    return;
+  RecordByteHistograms();
+}
+
+void MediaPageLoadMetricsObserver::OnLoadingBehaviorObserved(
+    const page_load_metrics::PageLoadExtraInfo& info) {
+  if (played_media_)
+    return;
+
+  played_media_ =
+      (info.metadata.behavior_flags &
+       blink::WebLoadingBehaviorFlag::WebLoadingBehaviorMediaPlayed) != 0;
+}
+
+void MediaPageLoadMetricsObserver::RecordByteHistograms() {
+  DCHECK(played_media_);
+  PAGE_BYTES_HISTOGRAM(kHistogramNetworkBytes, network_bytes_);
+  PAGE_BYTES_HISTOGRAM(kHistogramCacheBytes, cache_bytes_);
+  PAGE_BYTES_HISTOGRAM(kHistogramTotalBytes, network_bytes_ + cache_bytes_);
+}