Adding synthetic field trial for DataReductionProxyEnabled

chrome/browser/metrics/metrics_service_accessor.cc

 // Copyright 2014 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/metrics/metrics_service_accessor.h"
 
 #include "chrome/browser/browser_process.h"
 #include "components/metrics/metrics_service.h"
 #include "components/metrics/metrics_service_observer.h"
+#include "components/variations/metrics_util.h"
 
 // static
 void MetricsServiceAccessor::AddMetricsServiceObserver(
     MetricsServiceObserver* observer) {
   MetricsService* metrics_service = g_browser_process->metrics_service();
   if (metrics_service)
     metrics_service->AddObserver(observer);
 }
 
 void MetricsServiceAccessor::RemoveMetricsServiceObserver(
     MetricsServiceObserver* observer) {
   MetricsService* metrics_service = g_browser_process->metrics_service();
   if (metrics_service)
     metrics_service->RemoveObserver(observer);
 }
+
+// static
+bool MetricsServiceAccessor::RegisterSyntheticFieldTrial(
+    MetricsService* metrics_service,
+    const std::string& trial,
+    const std::string& group) {
+  if (metrics_service) {

[Alexei Svitkine (slow), 2014/07/30 21:33:31]

Nit: Instead do an early return if the service is nil (reverse the if).

[megjablon, 2014/07/30 21:42:50]

Done.

+    SyntheticTrialGroup trial_group(metrics::HashName(trial),
+                                    metrics::HashName(group));
+    metrics_service->RegisterSyntheticFieldTrial(trial_group);
+    return true;
+  }
+  return false;
+}