Reset some UMA stability stats on a version change.

chrome/browser/metrics/chrome_stability_metrics_provider.h

 // Copyright 2014 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_METRICS_CHROME_STABILITY_METRICS_PROVIDER_H_
 #define CHROME_BROWSER_METRICS_CHROME_STABILITY_METRICS_PROVIDER_H_
 
 #include "base/basictypes.h"
 #include "base/metrics/user_metrics.h"
 #include "base/process/kill.h"
@@ skipping 17 matching lines @@
       public content::NotificationObserver {
  public:
   ChromeStabilityMetricsProvider();
   virtual ~ChromeStabilityMetricsProvider();
 
   // metrics::MetricsDataProvider:
   virtual void OnRecordingEnabled() OVERRIDE;
   virtual void OnRecordingDisabled() OVERRIDE;
   virtual void ProvideStabilityMetrics(
       metrics::SystemProfileProto* system_profile_proto) OVERRIDE;
+  virtual void ClearSavedStabilityMetrics() OVERRIDE;
 
   // Registers local state prefs used by this class.
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
  private:
   // content::NotificationObserver:
   virtual void Observe(int type,
                        const content::NotificationSource& source,
                        const content::NotificationDetails& details) OVERRIDE;
 
@@ skipping 13 matching lines @@
   // Records a renderer process hang.
   void LogRendererHang();
 
   // Registrar for receiving stability-related notifications.
   content::NotificationRegistrar registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeStabilityMetricsProvider);
 };
 
 #endif  // CHROME_BROWSER_METRICS_CHROME_STABILITY_METRICS_PROVIDER_H_