Update from https://crrev.com/304715

net/http/transport_security_state.cc

 // Copyright (c) 2012 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 "net/http/transport_security_state.h"
 
 #if defined(USE_OPENSSL)
 #include <openssl/ecdsa.h>
 #include <openssl/ssl.h>
 #else  // !defined(USE_OPENSSL)
 #include <cryptohi.h>
 #include <hasht.h>
 #include <keyhi.h>
 #include <nspr.h>
 #include <pk11pub.h>
 #endif
 
 #include <algorithm>
 
 #include "base/base64.h"
 #include "base/build_time.h"
 #include "base/logging.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
 #include "base/sha1.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
 #include "base/time/time.h"
 #include "base/values.h"
 #include "crypto/sha2.h"
 #include "net/base/dns_util.h"
 #include "net/cert/x509_cert_types.h"
 #include "net/cert/x509_certificate.h"
@@ skipping 681 matching lines @@
 // static
 void TransportSecurityState::ReportUMAOnPinFailure(const std::string& host) {
   PreloadResult result;
   if (!DecodeHSTSPreload(host, &result) ||
       !result.has_pins) {
     return;
   }
 
   DCHECK(result.domain_id != DOMAIN_NOT_PINNED);
 
-  UMA_HISTOGRAM_ENUMERATION(
-      "Net.PublicKeyPinFailureDomain", result.domain_id, DOMAIN_NUM_EVENTS);
+  UMA_HISTOGRAM_SPARSE_SLOWLY(
+      "Net.PublicKeyPinFailureDomain", result.domain_id);
 }
 
 // static
 bool TransportSecurityState::IsBuildTimely() {
   // If the build metadata aren't embedded in the binary then we can't use the
   // build time to determine if the build is timely, return true by default. If
   // we're building an official build then keep using the build time, even if
   // it's invalid it'd be a date in the past and this function will return
   // false.
 #if defined(DONT_EMBED_BUILD_METADATA) && !defined(OFFICIAL_BUILD)
@@ skipping 178 matching lines @@
   return pkp.spki_hashes.size() > 0 || pkp.bad_spki_hashes.size() > 0;
 }
 
 TransportSecurityState::DomainState::PKPState::PKPState() {
 }
 
 TransportSecurityState::DomainState::PKPState::~PKPState() {
 }
 
 }  // namespace