Add metrics for user manually added exceptions

components/content_settings/core/browser/host_content_settings_map.h

Index: components/content_settings/core/browser/host_content_settings_map.h
diff --git a/components/content_settings/core/browser/host_content_settings_map.h b/components/content_settings/core/browser/host_content_settings_map.h
index 17d9e126481f3c1910ff9b54f18441a9a880663b..aaeec546f247a6ecde6bfae275f527a6674bf456 100644
--- a/components/content_settings/core/browser/host_content_settings_map.h
+++ b/components/content_settings/core/browser/host_content_settings_map.h
@@ -306,6 +306,9 @@ class HostContentSettingsMap : public content_settings::Observer,
   // leave in some code to remove old-format settings for a long time.
   void MigrateOldSettings();
 
+  // Collect uma data of number of exceptions.
+  void CollectExceptionNumberUma();
+
   // Adds content settings for |content_type| and |resource_identifier|,
   // provided by |provider|, into |settings|. If |incognito| is true, adds only
   // the content settings which are applicable to the incognito mode and differ