Update from https://crrev.com/327068

base/prefs/pref_registry.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 "base/prefs/pref_registry.h"
 
 #include "base/logging.h"
 #include "base/prefs/default_pref_store.h"
 #include "base/prefs/pref_store.h"
+#include "base/stl_util.h"
 #include "base/values.h"
 
 PrefRegistry::PrefRegistry()
     : defaults_(new DefaultPrefStore()) {
 }
 
 PrefRegistry::~PrefRegistry() {
 }
 
+uint32 PrefRegistry::GetRegistrationFlags(const std::string& pref_name) const {
+  const auto& it = registration_flags_.find(pref_name);
+  if (it == registration_flags_.end())
+    return NO_REGISTRATION_FLAGS;
+  return it->second;
+}
+
 scoped_refptr<PrefStore> PrefRegistry::defaults() {
   return defaults_.get();
 }
 
 PrefRegistry::const_iterator PrefRegistry::begin() const {
   return defaults_->begin();
 }
 
 PrefRegistry::const_iterator PrefRegistry::end() const {
   return defaults_->end();
 }
 
 void PrefRegistry::SetDefaultPrefValue(const std::string& pref_name,
                                        base::Value* value) {
   DCHECK(value);
   const base::Value* current_value = NULL;
   DCHECK(defaults_->GetValue(pref_name, &current_value))
       << "Setting default for unregistered pref: " << pref_name;
   DCHECK(value->IsType(current_value->GetType()))
       << "Wrong type for new default: " << pref_name;
 
   defaults_->ReplaceDefaultValue(pref_name, make_scoped_ptr(value));
 }
 
 void PrefRegistry::RegisterPreference(const std::string& path,
-                                      base::Value* default_value) {
+                                      base::Value* default_value,
+                                      uint32 flags) {
   base::Value::Type orig_type = default_value->GetType();
   DCHECK(orig_type != base::Value::TYPE_NULL &&
          orig_type != base::Value::TYPE_BINARY) <<
          "invalid preference type: " << orig_type;
   DCHECK(!defaults_->GetValue(path, NULL)) <<
       "Trying to register a previously registered pref: " << path;
+  DCHECK(!ContainsKey(registration_flags_, path)) <<
+      "Trying to register a previously registered pref: " << path;
 
   defaults_->SetDefaultValue(path, make_scoped_ptr(default_value));
+  if (flags != NO_REGISTRATION_FLAGS)
+    registration_flags_[path] = flags;
 }