Write "logout-started" event on next boot.

chrome/browser/chromeos/boot_times_loader.h

Index: chrome/browser/chromeos/boot_times_loader.h
diff --git a/chrome/browser/chromeos/boot_times_loader.h b/chrome/browser/chromeos/boot_times_loader.h
index 854dccdabee2898f80009517cdd8fca85ef657b2..81e4776e3d1e52b60d8e196132743a253be2ed2c 100644
--- a/chrome/browser/chromeos/boot_times_loader.h
+++ b/chrome/browser/chromeos/boot_times_loader.h
@@ -17,6 +17,8 @@
 #include "content/public/browser/notification_registrar.h"
 #include "content/public/browser/render_widget_host.h"
 
+class PrefService;
+
 namespace chromeos {
 
 // BootTimesLoader loads the bootimes of Chrome OS from the file system.
@@ -82,6 +84,12 @@ class BootTimesLoader : public content::NotificationObserver {
   // Mark that WriteLogoutTimes should handle restart.
   void set_restart_requested() { restart_requested_ = true; }
 
+  // This is called on Chrome process startup to write saved logout stats.
+  void OnBoot();

[stevenjb, 2014/05/30 16:20:23]

"Boot" is rather unspecific, could you give this a more descriptive name, e.g.
"OnProfileCreated"?

[Alexander Alekseev, 2014/05/30 21:12:45]

There are many different OnProfileCreated events.
Let it be OnChromeProcessStart().

+
+  // This saves logout-started metric to Local State.
+  void OnLogoutStarted(PrefService* state);
+
  private:
   // BootTimesLoader calls into the Backend on the file thread to load
   // the boot times.
@@ -121,19 +129,30 @@ class BootTimesLoader : public content::NotificationObserver {
 
   struct Stats {
    public:
+    std::string SerializeToString() const;
+    static Stats DeserializeFromString(const std::string& value);
+
     std::string uptime;
     std::string disk;
   };
 
   static void RecordStats(
       const std::string& name, const Stats& stats);
+  void RecordStatsWithCallback(const std::string& name,
+                               const Stats& stats,
+                               const base::Closure& callback);
   static Stats GetCurrentStats();
+  static std::string GetUptimeSeconds(const Stats& stats);
   static void WriteTimes(const std::string base_name,
                          const std::string uma_name,
                          const std::string uma_prefix,
                          std::vector<TimeMarker> login_times);
   static void AddMarker(std::vector<TimeMarker>* vector, TimeMarker marker);
 
+  // Clear saved logout-started metric in Local State.
+  // This method is called when logout-state was writen to file.
+  static void ClearLogoutStartedLastPreference();
+
   // Used to hold the stats at main().
   Stats chrome_main_stats_;
   scoped_refptr<Backend> backend_;