Adding local field trial for metrics/crash reports sampling.

chrome/browser/chrome_browser_main.cc

 // Copyright (c) 2012 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/chrome_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 889 matching lines @@
 #if defined(FIELDTRIAL_TESTING_ENABLED)
   if (!command_line->HasSwitch(switches::kDisableFieldTrialTestingConfig) &&
       !command_line->HasSwitch(switches::kForceFieldTrials) &&
       !command_line->HasSwitch(variations::switches::kVariationsServerURL)) {
     chrome_variations::AssociateDefaultFieldTrialConfig(feature_list.get());
   }
 #endif  // defined(FIELDTRIAL_TESTING_ENABLED)
 
   variations::VariationsService* variations_service =
       browser_process_->variations_service();
-  if (variations_service)
-    variations_service->CreateTrialsFromSeed(feature_list.get());
+  bool has_seed = false;

[Lei Zhang, 2016/08/30 21:31:28]

How about:

bool has_seed = variations_service && variations_service->Foo();

and then "let git cl format" make it pretty?

[jwd, 2016/08/30 21:46:24]

Done.

+  if (variations_service) {
+    has_seed = variations_service->CreateTrialsFromSeed(feature_list.get());
+  }
+
+  browser_field_trials_.SetupFeatureControllingFieldTrials(has_seed,
+                                                           feature_list.get());
 
   base::FeatureList::SetInstance(std::move(feature_list));
 
   // This must be called after |local_state_| is initialized.
   browser_field_trials_.SetupFieldTrials();
 
   // Enable Navigation Tracing only if a trace upload url is specified.
   if (command_line->HasSwitch(switches::kEnableNavigationTracing) &&
       command_line->HasSwitch(switches::kTraceUploadURL)) {
     tracing::SetupNavigationTracing();
@@ skipping 1308 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }