Define a new policy to disable clearing the browsing history from the UI.

chrome/browser/ui/webui/settings/settings_clear_browsing_data_handler.cc

 // Copyright 2015 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 "chrome/browser/ui/webui/settings/settings_clear_browsing_data_handler.h"
 
 #include <stddef.h>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ skipping 82 matching lines @@
       base::Bind(&ClearBrowsingDataHandler::HandleClearBrowsingData,
                  base::Unretained(this)));
 
   web_ui()->RegisterMessageCallback(
       "initializeClearBrowsingData",
       base::Bind(&ClearBrowsingDataHandler::HandleInitialize,
                  base::Unretained(this)));
 }
 
 void ClearBrowsingDataHandler::OnJavascriptAllowed() {
-  PrefService* prefs = profile_->GetPrefs();
-  profile_pref_registrar_.Init(prefs);
-  profile_pref_registrar_.Add(
-      prefs::kAllowDeletingBrowserHistory,
-      base::Bind(&ClearBrowsingDataHandler::OnBrowsingHistoryPrefChanged,
-                 base::Unretained(this)));
-
   if (sync_service_)
     sync_service_observer_.Add(sync_service_);
 
   DCHECK(counters_.empty());
   for (const std::string& pref : kCounterPrefs) {
     AddCounter(
         BrowsingDataCounterFactory::GetForProfileAndPref(profile_, pref));
   }
 }
 
 void ClearBrowsingDataHandler::OnJavascriptDisallowed() {
-  profile_pref_registrar_.RemoveAll();
   sync_service_observer_.RemoveAll();
   task_observer_.reset();
   counters_.clear();
 }
 
 void ClearBrowsingDataHandler::HandleClearBrowsingData(
     const base::ListValue* args) {
   DCHECK(!task_observer_);
 
   PrefService* prefs = profile_->GetPrefs();
@@ skipping 113 matching lines @@
 
   UMA_HISTOGRAM_BOOLEAN(
       "History.ClearBrowsingData.ShownHistoryNoticeAfterClearing", show_notice);
 
   ResolveJavascriptCallback(
       base::StringValue(webui_callback_id),
       base::FundamentalValue(show_notice));
   task_observer_.reset();
 }
 
-void ClearBrowsingDataHandler::OnBrowsingHistoryPrefChanged() {
-  CallJavascriptFunction(
-      "cr.webUIListenerCallback",
-      base::StringValue("browsing-history-pref-changed"),
-      base::FundamentalValue(
-          profile_->GetPrefs()->GetBoolean(
-              prefs::kAllowDeletingBrowserHistory)));
-}
-
 void ClearBrowsingDataHandler::HandleInitialize(const base::ListValue* args) {
   AllowJavascript();
   const base::Value* callback_id;
   CHECK(args->Get(0, &callback_id));
 
   // Needed because WebUI doesn't handle renderer crashes. See crbug.com/610450.
   task_observer_.reset();
 
   OnStateChanged();
   RefreshHistoryNotice();
@@ skipping 60 matching lines @@
 void ClearBrowsingDataHandler::UpdateCounterText(
     std::unique_ptr<browsing_data::BrowsingDataCounter::Result> result) {
   CallJavascriptFunction(
       "cr.webUIListenerCallback",
       base::StringValue("update-counter-text"),
       base::StringValue(result->source()->GetPrefName()),
       base::StringValue(GetChromeCounterTextFromResult(result.get())));
 }
 
 }  // namespace settings