Update from https://crrev.com/306655

base/prefs/pref_change_registrar.cc

 // Copyright (c) 2010 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_change_registrar.h"
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/prefs/pref_service.h"
 
 PrefChangeRegistrar::PrefChangeRegistrar() : service_(NULL) {}
 
 PrefChangeRegistrar::~PrefChangeRegistrar() {
   // If you see an invalid memory access in this destructor, this
   // PrefChangeRegistrar might be subscribed to an OffTheRecordProfileImpl that
   // has been destroyed. This should not happen any more but be warned.
   // Feel free to contact battre@chromium.org in case this happens.
   RemoveAll();
 }
 
 void PrefChangeRegistrar::Init(PrefService* service) {
   DCHECK(IsEmpty() || service_ == service);
   service_ = service;
 }
 
-void PrefChangeRegistrar::Add(const char* path,
+void PrefChangeRegistrar::Add(const std::string& path,
                               const base::Closure& obs) {
   Add(path, base::Bind(&PrefChangeRegistrar::InvokeUnnamedCallback, obs));
 }
 
-void PrefChangeRegistrar::Add(const char* path,
+void PrefChangeRegistrar::Add(const std::string& path,
                               const NamedChangeCallback& obs) {
   if (!service_) {
     NOTREACHED();
     return;
   }
   DCHECK(!IsObserved(path)) << "Already had this pref registered.";
 
   service_->AddPrefObserver(path, this);
   observers_[path] = obs;
 }
 
-void PrefChangeRegistrar::Remove(const char* path) {
+void PrefChangeRegistrar::Remove(const std::string& path) {
   DCHECK(IsObserved(path));
 
   observers_.erase(path);
   service_->RemovePrefObserver(path, this);
 }
 
 void PrefChangeRegistrar::RemoveAll() {
   for (ObserverMap::const_iterator it = observers_.begin();
        it != observers_.end(); ++it) {
-    service_->RemovePrefObserver(it->first.c_str(), this);
+    service_->RemovePrefObserver(it->first, this);
   }
 
   observers_.clear();
 }
 
 bool PrefChangeRegistrar::IsEmpty() const {
   return observers_.empty();
 }
 
 bool PrefChangeRegistrar::IsObserved(const std::string& pref) {
   return observers_.find(pref) != observers_.end();
 }
 
 bool PrefChangeRegistrar::IsManaged() {
   for (ObserverMap::const_iterator it = observers_.begin();
        it != observers_.end(); ++it) {
-    const PrefService::Preference* pref =
-        service_->FindPreference(it->first.c_str());
+    const PrefService::Preference* pref = service_->FindPreference(it->first);
     if (pref && pref->IsManaged())
       return true;
   }
   return false;
 }
 
 void PrefChangeRegistrar::OnPreferenceChanged(PrefService* service,
                                               const std::string& pref) {
   if (IsObserved(pref))
     observers_[pref].Run(pref);
 }
 
 void PrefChangeRegistrar::InvokeUnnamedCallback(const base::Closure& callback,
                                                 const std::string& pref_name) {
   callback.Run();
 }
 
 PrefService* PrefChangeRegistrar::prefs() {
   return service_;
 }
 
 const PrefService* PrefChangeRegistrar::prefs() const {
   return service_;
 }