Make Sber1/2 pref metrics into Nullable Booleans so we can track how often these prefs are unset.

chrome/browser/profiles/profile.cc

Index: chrome/browser/profiles/profile.cc
diff --git a/chrome/browser/profiles/profile.cc b/chrome/browser/profiles/profile.cc
index 5dc721b6508f61918cfdf47d16aa0691ade01907..16fea3cb6e8be834a43f07e6321ae172bf1db4e8 100644
--- a/chrome/browser/profiles/profile.cc
+++ b/chrome/browser/profiles/profile.cc
@@ -100,6 +100,10 @@ void Profile::RegisterProfilePrefs(user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterBooleanPref(prefs::kSafeBrowsingScoutReportingEnabled,
                                 false);
   registry->RegisterBooleanPref(prefs::kSafeBrowsingScoutGroupSelected, false);
+  registry->RegisterBooleanPref(
+      prefs::kSafeBrowsingSawInterstitialExtendedReporting, false);
+  registry->RegisterBooleanPref(
+      prefs::kSafeBrowsingSawInterstitialScoutReporting, false);
   registry->RegisterBooleanPref(prefs::kSafeBrowsingProceedAnywayDisabled,
                                 false);
   registry->RegisterBooleanPref(prefs::kSSLErrorOverrideAllowed, true);