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

ios/chrome/browser/ssl/ios_ssl_blocking_page.mm

 // Copyright 2016 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 "ios/chrome/browser/ssl/ios_ssl_blocking_page.h"
 
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram.h"
@@ skipping 22 matching lines @@
 enum SSLExpirationAndDecision {
   EXPIRED_AND_PROCEED,
   EXPIRED_AND_DO_NOT_PROCEED,
   NOT_EXPIRED_AND_PROCEED,
   NOT_EXPIRED_AND_DO_NOT_PROCEED,
   END_OF_SSL_EXPIRATION_AND_DECISION,
 };
 
 // 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,
                                        bool overridable) {
   SSLExpirationAndDecision event;
   if (expired_but_previously_allowed && proceed)
     event = EXPIRED_AND_PROCEED;
   else if (expired_but_previously_allowed && !proceed)
     event = EXPIRED_AND_DO_NOT_PROCEED;
   else if (!expired_but_previously_allowed && proceed)
@@ skipping 154 matching lines @@
   callback_.Reset();
 }
 
 // static
 bool IOSSSLBlockingPage::IsOverridable(int options_mask) {
   const bool is_overridable =
       (options_mask & SSLErrorUI::SOFT_OVERRIDE_ENABLED) &&
       !(options_mask & SSLErrorUI::STRICT_ENFORCEMENT);
   return is_overridable;
 }