Domain Reliability: Add sample_rate field to Beacon

components/domain_reliability/context.cc

Index: components/domain_reliability/context.cc
diff --git a/components/domain_reliability/context.cc b/components/domain_reliability/context.cc
index f0ce6c54c624cb15f1273495d72d5b9c84cc1a83..bcd0d7fc8907845f2c0d99f98b4b811ba39505df 100644
--- a/components/domain_reliability/context.cc
+++ b/components/domain_reliability/context.cc
@@ -11,6 +11,7 @@
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
+#include "base/rand_util.h"
 #include "base/values.h"
 #include "components/domain_reliability/dispatcher.h"
 #include "components/domain_reliability/uploader.h"
@@ -69,16 +70,17 @@ DomainReliabilityContext::~DomainReliabilityContext() {
 void DomainReliabilityContext::OnBeacon(
     scoped_ptr<DomainReliabilityBeacon> beacon) {
   bool success = (beacon->status == "ok");
-
-  bool reported = config().DecideIfShouldReportRequest(success);
-  UMA_HISTOGRAM_BOOLEAN("DomainReliability.BeaconReported", reported);
-  if (!reported) {
+  double sample_rate = config().GetSampleRate(success);
+  bool report = base::RandDouble() < sample_rate;

[jkarlin, 2015/12/09 11:46:22]

nit: s/report/should_report/

report sounds like an object, not a bool

[Deprecated (see juliatuttle), 2015/12/10 17:04:23]

Done, and same for evicted => should_evict.

+  UMA_HISTOGRAM_BOOLEAN("DomainReliability.BeaconReported", report);
+  if (!report) {
     // If the beacon isn't queued to be reported, it definitely cannot evict
     // an older beacon. (This histogram is also logged below based on whether
     // an older beacon was actually evicted.)
     LogOnBeaconDidEvictHistogram(false);
     return;
   }
+  beacon->sample_rate = sample_rate;
 
   UMA_HISTOGRAM_SPARSE_SLOWLY("DomainReliability.ReportedBeaconError",
                               -beacon->chrome_error);