Add UMA metrics to the site engagement service.

chrome/browser/engagement/site_engagement_metrics.cc

+// Copyright 2015 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/engagement/site_engagement_metrics.h"
+
+#include "base/metrics/histogram_macros.h"
+#include "base/metrics/sparse_histogram.h"
+
+const char SiteEngagementMetrics::kTotalEngagementHistogram[] =
+    "SiteEngagementService.TotalEngagement";
+
+const char SiteEngagementMetrics::kTotalOriginsHistogram[] =
+    "SiteEngagementService.OriginsEngaged";
+
+const char SiteEngagementMetrics::kEngagementScoreHistogram[] =
+    "SiteEngagementService.EngagementScore";
+
+const char SiteEngagementMetrics::kOriginsWithMaxEngagementHistogram[] =
+    "SiteEngagementService.OriginsWithMaxEngagement";
+
+const char SiteEngagementMetrics::kOriginsWithMaxDailyEngagementHistogram[] =
+    "SiteEngagementService.OriginsWithMaxDailyEngagement";
+
+const char SiteEngagementMetrics::kEngagementTypeHistogram[] =
+    "SiteEngagementService.EngagementType";
+
+void SiteEngagementMetrics::RecordTotalSiteEngagement(
+    double total_engagement) {
+  UMA_HISTOGRAM_COUNTS_10000(kTotalEngagementHistogram, total_engagement);
+}
+
+void SiteEngagementMetrics::RecordTotalOriginsEngaged(int num_origins) {
+  UMA_HISTOGRAM_COUNTS_10000(kTotalOriginsHistogram, num_origins);
+}
+
+void SiteEngagementMetrics::RecordEngagementScore(
+    std::map<GURL, double> score_map) {
+  for (const auto& value: score_map) {
+    UMA_HISTOGRAM_COUNTS_100(kEngagementScoreHistogram, value.second);
+  }
+}
+
+void SiteEngagementMetrics::RecordOriginsWithMaxEngagement(int total_origins) {
+  UMA_HISTOGRAM_COUNTS_100(kOriginsWithMaxEngagementHistogram, total_origins);
+}
+
+void SiteEngagementMetrics::RecordOriginsWithMaxDailyEngagement(
+    int total_origins) {
+  UMA_HISTOGRAM_COUNTS_100(kOriginsWithMaxDailyEngagementHistogram,
+                           total_origins);
+}
+
+void SiteEngagementMetrics::RecordEngagement(EngagementType type) {
+  switch (type) {
+    case ENGAGEMENT_NAVIGATION:
+      UMA_HISTOGRAM_SPARSE_SLOWLY(kEngagementTypeHistogram,

[benwells, 2015/09/30 00:10:54]

Reading
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/f-fO6I5UleU
I think this is the wrong macro to use.

[Ilya Sherman, 2015/10/01 07:08:17]

It's fine either way, but yeah, UMA_HISTOGRAM_ENUMERATION is probably a little
better suited for this tiny enum.

[dominickn, 2015/10/01 08:19:44]

Done.

+                                  ENGAGEMENT_NAVIGATION);
+      break;
+    case ENGAGEMENT_KEYPRESS:
+      UMA_HISTOGRAM_SPARSE_SLOWLY(kEngagementTypeHistogram,
+                                  ENGAGEMENT_KEYPRESS);
+      break;
+    case ENGAGEMENT_MOUSE:
+      UMA_HISTOGRAM_SPARSE_SLOWLY(kEngagementTypeHistogram, ENGAGEMENT_MOUSE);

[Ilya Sherman, 2015/10/01 07:08:17]

nit: Please move the UMA_HISTOGRAM_ macro out of the switch stmt, so that the
switch stmt just sets the metric that should be emitted.  (i.e., please don't
repeat this line three times.)

[dominickn, 2015/10/01 08:19:44]

Done.

+      break;
+    default:

[Ilya Sherman, 2015/10/01 07:08:17]

nit: Please remove the default case: the compiler should be able to enforce that
all cases are covered, but only if you remove the default case.

[dominickn, 2015/10/01 08:19:44]

Done.

+      NOTREACHED() << "Invalid type passed to RecordUserInput().";
+      break;
+  }
+}