Reset some UMA stability stats on a version change.

chrome/browser/metrics/chrome_stability_metrics_provider.cc

 // 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.
 
 #include "chrome/browser/metrics/chrome_stability_metrics_provider.h"
 
 #include <vector>
 
 #include "base/logging.h"
 #include "base/metrics/histogram.h"
@@ skipping 108 matching lines @@
     pref->SetInteger(prefs::kStabilityExtensionRendererCrashCount, 0);
   }
 
   count = pref->GetInteger(prefs::kStabilityRendererHangCount);
   if (count) {
     stability_proto->set_renderer_hang_count(count);
     pref->SetInteger(prefs::kStabilityRendererHangCount, 0);
   }
 }
 
+void ChromeStabilityMetricsProvider::ClearSavedStabilityMetrics() {
+  PrefService* local_state = g_browser_process->local_state();
+
+  // Clear all the prefs used in this class in UMA reports (which doesn't
+  // include |kUninstallMetricsPageLoadCount| as it's not sent up by UMA).
+  local_state->SetInteger(prefs::kStabilityChildProcessCrashCount, 0);
+  local_state->SetInteger(prefs::kStabilityExtensionRendererCrashCount, 0);
+  local_state->SetInteger(prefs::kStabilityPageLoadCount, 0);
+  local_state->SetInteger(prefs::kStabilityRendererCrashCount, 0);
+  local_state->SetInteger(prefs::kStabilityRendererHangCount, 0);
+}
+
 // static
 void ChromeStabilityMetricsProvider::RegisterPrefs(
     PrefRegistrySimple* registry) {
+  registry->RegisterIntegerPref(prefs::kStabilityChildProcessCrashCount, 0);
+  registry->RegisterIntegerPref(prefs::kStabilityExtensionRendererCrashCount,
+                                0);
   registry->RegisterIntegerPref(prefs::kStabilityPageLoadCount, 0);
   registry->RegisterIntegerPref(prefs::kStabilityRendererCrashCount, 0);
-  registry->RegisterIntegerPref(prefs::kStabilityExtensionRendererCrashCount,
-                                0);
   registry->RegisterIntegerPref(prefs::kStabilityRendererHangCount, 0);
-  registry->RegisterIntegerPref(prefs::kStabilityChildProcessCrashCount, 0);
+
   registry->RegisterInt64Pref(prefs::kUninstallMetricsPageLoadCount, 0);
 }
 
 void ChromeStabilityMetricsProvider::Observe(
     int type,
     const content::NotificationSource& source,
     const content::NotificationDetails& details) {
   switch (type) {
     case content::NOTIFICATION_LOAD_START: {
       content::NavigationController* controller =
@@ skipping 78 matching lines @@
                              was_extension_process ? 2 : 1);
   } else if (status == base::TERMINATION_STATUS_STILL_RUNNING) {
     UMA_HISTOGRAM_PERCENTAGE("BrowserRenderProcessHost.DisconnectedAlive",
                              was_extension_process ? 2 : 1);
   }
 }
 
 void ChromeStabilityMetricsProvider::LogRendererHang() {
   IncrementPrefValue(prefs::kStabilityRendererHangCount);
 }