Support experiment configurations with/without stability metrics.

components/metrics/file_metrics_provider.h

Index: components/metrics/file_metrics_provider.h
diff --git a/components/metrics/file_metrics_provider.h b/components/metrics/file_metrics_provider.h
index ba2e9f9571a0a9bc0734a9a676804d7015588bd1..c0a9b8c120ea774c86ca9b2b7e0d68a14b1dd200 100644
--- a/components/metrics/file_metrics_provider.h
+++ b/components/metrics/file_metrics_provider.h
@@ -101,6 +101,12 @@ class FileMetricsProvider : public MetricsProvider {
   static void RegisterPrefs(PrefRegistrySimple* prefs,
                             const base::StringPiece prefs_key);
 
+  // Allow stability metrics support (those found in a file for a previous run
+  // of the browser) to be enabled/disabled. By default it is enabled.
+  static void set_stability_metrics_enabled(bool enabled) {
+    stability_metrics_enabled_ = enabled;
+  }
+
  private:
   friend class FileMetricsProviderTest;
 
@@ -196,6 +202,9 @@ class FileMetricsProvider : public MetricsProvider {
   base::ThreadChecker thread_checker_;
   base::WeakPtrFactory<FileMetricsProvider> weak_factory_;
 
+  // Flag indicating if stability metrics are enabled or disabled.
+  static bool stability_metrics_enabled_;
+
   DISALLOW_COPY_AND_ASSIGN(FileMetricsProvider);
 };