Log operator code histogram on new metric log

chrome/browser/metrics/metrics_service.h

Index: chrome/browser/metrics/metrics_service.h
diff --git a/chrome/browser/metrics/metrics_service.h b/chrome/browser/metrics/metrics_service.h
index 82c3c30d6f8146a804ebafab5696be2e6d018a68..4e214e57f870e266b19a4d7936b44115f0be32f7 100644
--- a/chrome/browser/metrics/metrics_service.h
+++ b/chrome/browser/metrics/metrics_service.h
@@ -18,6 +18,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/user_metrics.h"
+#include "base/observer_list.h"
 #include "base/process/kill.h"
 #include "base/time/time.h"
 #include "chrome/browser/metrics/metrics_log.h"
@@ -36,6 +37,7 @@
 #include "chrome/browser/chromeos/external_metrics.h"
 #endif
 
+class ChromeBrowserMetricsLogObserver;
 class MetricsReportingScheduler;
 class PrefService;
 class PrefRegistrySimple;
@@ -108,6 +110,19 @@ struct SyntheticTrialGroup {
   SyntheticTrialGroup(uint32 trial, uint32 group);
 };
 
+class MetricsLogObserver {
+ public:
+  // Will be called when a new MetricsLog is created.
+  virtual void OnNewMetricsLog() = 0;
+
+ protected:
+  MetricsLogObserver() {}
+  virtual ~MetricsLogObserver() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(MetricsLogObserver);
+};
+
 class MetricsService
     : public chrome_browser_metrics::TrackingSynchronizerObserver,
       public content::BrowserChildProcessObserver,
@@ -402,6 +417,11 @@ class MetricsService
   // Generates a new client ID to use to identify self to metrics server.
   static std::string GenerateClientID();
 
+  // Registers/Unregsiters |observer| to receive MetricsLog notifications.
+  void AddMetricsLogObserver(MetricsLogObserver* observer);
+  void RemoveMetricsLogObserver(MetricsLogObserver* observer);
+  void NotifyOnNewMetricsLog();
+
   // Schedule the next save of LocalState information.  This is called
   // automatically by the task that performs each save to schedule the next one.
   void ScheduleNextStateSave();
@@ -628,8 +648,13 @@ class MetricsService
   // Field trial groups that map to Chrome configuration states.
   SyntheticTrialGroups synthetic_trial_groups_;
 
+  // Observers of MetricsLog.
+  ObserverList<MetricsLogObserver> metrics_log_observers_;
+
   scoped_ptr<metrics::ClonedInstallDetector> cloned_install_detector_;
 
+  friend class MetricsServiceHelper;
+
   FRIEND_TEST_ALL_PREFIXES(MetricsServiceTest, ClientIdCorrectlyFormatted);
   FRIEND_TEST_ALL_PREFIXES(MetricsServiceTest, IsPluginProcess);
   FRIEND_TEST_ALL_PREFIXES(MetricsServiceTest, LowEntropySource0NotReset);
@@ -645,13 +670,14 @@ class MetricsService
   DISALLOW_COPY_AND_ASSIGN(MetricsService);
 };
 
-// This class limits and documents access to the IsMetricsReportingEnabled() and
-// IsCrashReportingEnabled() methods. Since these methods are private, each user
-// has to be explicitly declared as a 'friend' below.
+// This class limits and documents access to metrics service helper methods.
+// Since these methods are private, each user has to be explicitly declared
+// as a 'friend' below.
 class MetricsServiceHelper {
  private:
   friend bool prerender::IsOmniboxEnabled(Profile* profile);
   friend class ChromeRenderMessageFilter;
+  friend class ::ChromeBrowserMetricsLogObserver;
   friend class ::CrashesDOMHandler;
   friend class extensions::ExtensionDownloader;
   friend class extensions::ManifestFetchData;
@@ -669,6 +695,11 @@ class MetricsServiceHelper {
   // IsMetricsReportingEnabled for desktop Chrome.
   static bool IsCrashReportingEnabled();
 
+  // Registers/Unregsiters |observer| to receive MetricsLog notifications
+  // from metric service.
+  static void AddMetricsLogObserver(MetricsLogObserver* observer);
+  static void RemoveMetricsLogObserver(MetricsLogObserver* observer);
+
   DISALLOW_IMPLICIT_CONSTRUCTORS(MetricsServiceHelper);
 };