Update API for recording interaction/decision enums in MetricsHelper

Update RecordSingleDecisionToMetrics and RecordSingleInteractionToMetrics
to use a simpler API, which now supports non-constant histogram names.

Change-Id: Iae63351d0ce6915841f48b614aad7a22f12839ac
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2347319Reviewed-by: Carlos IL <carlosil@chromium.org>
Commit-Queue: Livvie Lin <livvielin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#796979}

components/security_interstitials/core/metrics_helper.cc

@@ -9,6 +9,7 @@
 
 #include "base/bind.h"
 #include "base/metrics/histogram.h"
+#include "base/metrics/histogram_functions.h"
 #include "base/metrics/user_metrics.h"
 #include "base/metrics/user_metrics_action.h"
 #include "components/history/core/browser/history_service.h"
@@ -21,25 +22,16 @@ namespace security_interstitials {
 
 namespace {
 
-// Directly adds to the UMA histograms, using the same properties as
-// UMA_HISTOGRAM_ENUMERATION, because the macro doesn't allow non-constant
-// histogram names.
 void RecordSingleDecisionToMetrics(MetricsHelper::Decision decision,
                                    const std::string& histogram_name) {
-  base::HistogramBase* histogram = base::LinearHistogram::FactoryGet(
-      histogram_name, 1, MetricsHelper::MAX_DECISION,
-      MetricsHelper::MAX_DECISION + 1,
-      base::HistogramBase::kUmaTargetedHistogramFlag);
-  histogram->Add(decision);
+  base::UmaHistogramExactLinear(histogram_name, decision,
+                                MetricsHelper::MAX_DECISION);
 }
 
 void RecordSingleInteractionToMetrics(MetricsHelper::Interaction interaction,
                                       const std::string& histogram_name) {
-  base::HistogramBase* histogram = base::LinearHistogram::FactoryGet(
-      histogram_name, 1, MetricsHelper::MAX_INTERACTION,
-      MetricsHelper::MAX_INTERACTION + 1,
-      base::HistogramBase::kUmaTargetedHistogramFlag);
-  histogram->Add(interaction);
+  base::UmaHistogramExactLinear(histogram_name, interaction,
+                                MetricsHelper::MAX_INTERACTION);
 }
 
 void MaybeRecordDecisionAsAction(MetricsHelper::Decision decision,