Add one-time randomization support for FieldTrial, and the ability to

chrome/browser/browser_main.h

 // Copyright (c) 2011 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.
 
 #ifndef CHROME_BROWSER_BROWSER_MAIN_H_
 #define CHROME_BROWSER_BROWSER_MAIN_H_
 #pragma once
 
 #include "base/basictypes.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/tracked_objects.h"
 
 class BrowserThread;
 class CommandLine;
+class FieldTrialSynchronizer;
 class HighResolutionTimerManager;
 struct MainFunctionParams;
 class MessageLoop;
 class MetricsService;
+class PrefService;
 
 namespace net {
 class NetworkChangeNotifier;
 }
 
 namespace ui {
 class SystemMonitor;
 }
 
 // BrowserMainParts:
@@ skipping 43 matching lines @@
   // instantiate the appropriate subclass.
   static BrowserMainParts* CreateBrowserMainParts(
       const MainFunctionParams& parameters);
 
   virtual ~BrowserMainParts();
 
   // Parts to be called by |BrowserMain()|.
   void EarlyInitialization();
   void MainMessageLoopStart();
 
-  void SetupFieldTrials();
+  // Constructs metrics service and does related initialization, including
+  // creation of field trials. Call only after labs have been converted to
+  // switches.
+  MetricsService* SetupMetricsAndFieldTrials(
+      const CommandLine& parsed_command_line,
+      PrefService* local_state);
 
  protected:
   explicit BrowserMainParts(const MainFunctionParams& parameters);
 
   // Accessors for data members (below) ----------------------------------------
   const MainFunctionParams& parameters() const {
     return parameters_;
   }
   const CommandLine& parsed_command_line() const {
     return parsed_command_line_;
@@ skipping 31 matching lines @@
   // A/B test for SSL False Start.
   void SSLFalseStartFieldTrial();
 
   // Used to initialize NSPR where appropriate.
   virtual void InitializeSSL() = 0;
 
   // Methods for |MainMessageLoopStart()| --------------------------------------
 
   void InitializeMainThread();
 
+  // Methods for |SetupMetricsAndFieldTrials()| --------------------------------
+
+  static MetricsService* InitializeMetrics(
+      const CommandLine& parsed_command_line,
+      const PrefService* local_state);
+
+  // Add an invocation of your field trial init function to this method.
+  void SetupFieldTrials(bool metrics_recording_enabled);
+
   // Members initialized on construction ---------------------------------------
 
   const MainFunctionParams& parameters_;
   const CommandLine& parsed_command_line_;
 
 #if defined(TRACK_ALL_TASK_OBJECTS)
   // Creating this object starts tracking the creation and deletion of Task
   // instance. This MUST be done before main_message_loop, so that it is
   // destroyed after the main_message_loop.
   tracked_objects::AutoTracking tracking_objects_;
 #endif
 
-  // Statistical testing infrastructure for the entire browser.
-  base::FieldTrialList field_trial_;
+  // Statistical testing infrastructure for the entire browser. NULL until
+  // SetupMetricsAndFieldTrials is called.
+  scoped_ptr<base::FieldTrialList> field_trial_list_;
 
   // Members initialized in |MainMessageLoopStart()| ---------------------------
   scoped_ptr<MessageLoop> main_message_loop_;
   scoped_ptr<ui::SystemMonitor> system_monitor_;
   scoped_ptr<HighResolutionTimerManager> hi_res_timer_manager_;
   scoped_ptr<net::NetworkChangeNotifier> network_change_notifier_;
   scoped_ptr<BrowserThread> main_thread_;
 
+  // Initialized in SetupMetricsAndFieldTrials.
+  scoped_refptr<FieldTrialSynchronizer> field_trial_synchronizer_;
+
   DISALLOW_COPY_AND_ASSIGN(BrowserMainParts);
 };
 
 
 // Perform platform-specific work that needs to be done after the main event
 // loop has ended.
 void DidEndMainMessageLoop();
 
 // Records the conditions that can prevent Breakpad from generating and
 // sending crash reports.  The presence of a Breakpad handler (after
 // attempting to initialize crash reporting) and the presence of a debugger
 // are registered with the UMA metrics service.
 void RecordBreakpadStatusUMA(MetricsService* metrics);
 
 // Displays a warning message if some minimum level of OS support is not
 // present on the current platform.
 void WarnAboutMinimumSystemRequirements();
 
 // Records the time from our process' startup to the present time in
 // the UMA histogram |metric_name|.
 void RecordBrowserStartupTime();
 
 #endif  // CHROME_BROWSER_BROWSER_MAIN_H_