Move EntropyProvider Source From MetricsService to MetricsServicesManager

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index 250dbb6c61e5b15c1b09bba90cff575c746d68cc..e18055d89cb5c8bc20ce118d7a438a14a0bad959 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -794,17 +794,14 @@ ChromeBrowserMainParts::~ChromeBrowserMainParts() {
 // This will be called after the command-line has been mutated by about:flags
 void ChromeBrowserMainParts::SetupMetricsAndFieldTrials() {
   TRACE_EVENT0("startup", "ChromeBrowserMainParts::SetupMetricsAndFieldTrials");
-  // 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).
 
   // Initialize FieldTrialList to support FieldTrials that use one-time
   // randomization.
-  metrics::MetricsService* metrics = browser_process_->metrics_service();
-
   DCHECK(!field_trial_list_);
   field_trial_list_.reset(
-      new base::FieldTrialList(metrics->CreateEntropyProvider().release()));
+      new base::FieldTrialList(browser_process_->GetMetricsServicesManager()
+                                   ->CreateEntropyProvider()

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

A nice and easy follow-up to this patch would be to fix FieldTrialList to take a
unique_ptr which would improve this code.

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

Agreed to that.

+                                   .release()));
 
   const base::CommandLine* command_line =
       base::CommandLine::ForCurrentProcess();
@@ -845,6 +842,11 @@ void ChromeBrowserMainParts::SetupMetricsAndFieldTrials() {
       about_flags::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 = browser_process_->metrics_service();
+
   variations::VariationsHttpHeaderProvider* http_header_provider =
       variations::VariationsHttpHeaderProvider::GetInstance();
   // Force the variation ids selected in chrome://flags and/or specified using