Move EntropyProvider Source From MetricsService to MetricsServicesManager

ios/chrome/browser/ios_chrome_main_parts.mm

Index: ios/chrome/browser/ios_chrome_main_parts.mm
diff --git a/ios/chrome/browser/ios_chrome_main_parts.mm b/ios/chrome/browser/ios_chrome_main_parts.mm
index a3ede343d21b4ec794dc59a4e44c0c30acfe2006..3bee3f1a0648e0e61ce6f6b3189d1f57104286bb 100644
--- a/ios/chrome/browser/ios_chrome_main_parts.mm
+++ b/ios/chrome/browser/ios_chrome_main_parts.mm
@@ -193,15 +193,13 @@ void IOSChromeMainParts::SetUpMetricsAndFieldTrials() {
   base::SetRecordActionTaskRunner(
       web::WebThread::GetTaskRunnerForThread(web::WebThread::UI));
 
-  // Must initialize metrics after labs have been converted into switches,
-  // but before field trials are set up (so that client ID is available for
-  // one-time randomized field trials).
-  metrics::MetricsService* metrics = application_context_->GetMetricsService();
-
   // Initialize FieldTrialList to support FieldTrials that use one-time
   // randomization.
+  DCHECK(!field_trial_list_);
   field_trial_list_.reset(
-      new base::FieldTrialList(metrics->CreateEntropyProvider().release()));
+      new base::FieldTrialList(application_context_->GetMetricsServicesManager()
+                                   ->CreateEntropyProvider()

[brettw, 2016/09/14 22:22:03]

Ditto with unfortunate unique_ptr usage.

[robliao, 2016/09/15 14:31:18]

Agreed.

+                                   .release()));
 
   const base::CommandLine* command_line =
       base::CommandLine::ForCurrentProcess();
@@ -225,6 +223,11 @@ void IOSChromeMainParts::SetUpMetricsAndFieldTrials() {
   std::vector<std::string> variation_ids =
       RegisterAllFeatureVariationParameters(&flags_storage, feature_list.get());
 
+  // Must initialize metrics after about:flags have been converted into
+  // switches, but before field trials are set up (so that client ID is
+  // available for one-time randomized field trials).
+  metrics::MetricsService* metrics = application_context_->GetMetricsService();
+
   variations::VariationsHttpHeaderProvider* http_header_provider =
       variations::VariationsHttpHeaderProvider::GetInstance();
   // Force the variation ids selected in chrome://flags and/or specified using