Add experiment to exercise AffiliationService with dummy data, plus add related UMA histograms.

components/password_manager/core/browser/affiliation_backend.cc

Index: components/password_manager/core/browser/affiliation_backend.cc
diff --git a/components/password_manager/core/browser/affiliation_backend.cc b/components/password_manager/core/browser/affiliation_backend.cc
index 51419319d80b740f2dc74c1b8418f6e27def6c73..429f221fcdee7728ae74e22df00f1b1fa88659f9 100644
--- a/components/password_manager/core/browser/affiliation_backend.cc
+++ b/components/password_manager/core/browser/affiliation_backend.cc
@@ -8,6 +8,7 @@
 
 #include "base/bind.h"
 #include "base/location.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/clock.h"
@@ -30,6 +31,7 @@ AffiliationBackend::AffiliationBackend(
       task_runner_(task_runner),
       clock_(time_source.Pass()),
       tick_clock_(time_tick_source.Pass()),
+      construction_time_(clock_->Now()),
       weak_ptr_factory_(this) {
   DCHECK_LT(base::Time(), clock_->Now());
 }
@@ -220,9 +222,28 @@ bool AffiliationBackend::OnCanSendNetworkRequest() {
   fetcher_.reset(AffiliationFetcher::Create(request_context_getter_.get(),
                                             requested_facet_uris, this));
   fetcher_->StartRequest();
+  ReportStatistics(requested_facet_uris.size());
   return true;
 }
 
+void AffiliationBackend::ReportStatistics(size_t requested_facet_uri_count) {
+  UMA_HISTOGRAM_COUNTS_100("AffiliationService.FetchSize",
+                           requested_facet_uri_count);
+
+  if (last_request_time_.is_null()) {
+    base::TimeDelta delay = clock_->Now() - construction_time_;
+    UMA_HISTOGRAM_CUSTOM_TIMES("AffiliationService.FirstFetchDelay", delay,
+                               base::TimeDelta::FromMicroseconds(1),
+                               base::TimeDelta::FromDays(7), 100);

[Ilya Sherman, 2015/04/21 00:38:05]

Hmm, do you really need such a large range?

[engedy, 2015/04/21 18:29:07]

I need quite a large range, but on second though, not this much indeed. Reduced
to 1 sec ... 3 days and to 50 buckets.

+  } else {
+    base::TimeDelta delay = clock_->Now() - construction_time_;
+    UMA_HISTOGRAM_CUSTOM_TIMES("AffiliationService.SubsequentFetchDelay", delay,
+                               base::TimeDelta::FromMicroseconds(1),
+                               base::TimeDelta::FromDays(7), 100);
+  }
+  last_request_time_ = clock_->Now();
+}
+
 void AffiliationBackend::SetThrottlerForTesting(
     scoped_ptr<AffiliationFetchThrottler> throttler) {
   throttler_ = throttler.Pass();