Add a low-frequency RAPPOR configuration, and use it for Safe Browsing and Permissions metrics.

ios/chrome/browser/ssl/ios_ssl_blocking_page.mm

Index: ios/chrome/browser/ssl/ios_ssl_blocking_page.mm
diff --git a/ios/chrome/browser/ssl/ios_ssl_blocking_page.mm b/ios/chrome/browser/ssl/ios_ssl_blocking_page.mm
index d283a95c256a5695cc2f7d2ceb775ac3b3371ffb..1416ae3d8a60553cf478cfcb1a82c02f9988cb06 100644
--- a/ios/chrome/browser/ssl/ios_ssl_blocking_page.mm
+++ b/ios/chrome/browser/ssl/ios_ssl_blocking_page.mm
@@ -40,7 +40,8 @@ enum SSLExpirationAndDecision {
 
 // Rappor prefix, which is used for both overridable and non-overridable
 // interstitials so we don't leak the "overridable" bit.
-const char kSSLRapporPrefix[] = "ssl2";
+const char kDeprecatedSSLRapporPrefix[] = "ssl2";
+const char kSSLRapporPrefix[] = "ssl3";
 
 void RecordSSLExpirationPageEventState(bool expired_but_previously_allowed,
                                        bool proceed,