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

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

 // 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.
 
 #ifndef CHROME_BROWSER_UI_WEBUI_SETTINGS_SETTINGS_CLEAR_BROWSING_DATA_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_SETTINGS_CLEAR_BROWSING_DATA_HANDLER_H_
 
 #include <memory>
 #include <string>
 #include <vector>
 
 #include "base/macros.h"
 #include "base/scoped_observer.h"
 #include "chrome/browser/browsing_data/browsing_data_remover.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/ui/webui/settings/settings_page_ui_handler.h"
 #include "components/browser_sync/profile_sync_service.h"
 #include "components/browsing_data/core/counters/browsing_data_counter.h"
-#include "components/prefs/pref_change_registrar.h"
 
 namespace base {
 class ListValue;
 }
 
 namespace content {
 class WebUI;
 }
 
 namespace settings {
@@ skipping 15 matching lines @@
   // Calls |callback| when the task is finished.
   class TaskObserver;
 
   // Clears browsing data, called by Javascript.
   void HandleClearBrowsingData(const base::ListValue* value);
 
   // Called when a clearing task finished. |webui_callback_id| is provided
   // by the WebUI action that initiated it.
   void OnClearingTaskFinished(const std::string& webui_callback_id);
 
-  // Updates UI when the pref to allow clearing history changes.
-  virtual void OnBrowsingHistoryPrefChanged();
-
   // Initializes the dialog UI. Called by JavaScript when the DOM is ready.
   void HandleInitialize(const base::ListValue* args);
 
   // Implementation of SyncServiceObserver. Updates the footer of the dialog
   // when the sync state changes.
   void OnStateChanged() override;
 
   // Finds out whether we should show notice about other forms of history stored
   // in user's account.
   void RefreshHistoryNotice();
@@ skipping 21 matching lines @@
   std::vector<std::unique_ptr<browsing_data::BrowsingDataCounter>> counters_;
 
   // Observes the currently active data clearing task.
   std::unique_ptr<TaskObserver> task_observer_;
 
   // ProfileSyncService to observe sync state changes.
   browser_sync::ProfileSyncService* sync_service_;
   ScopedObserver<browser_sync::ProfileSyncService, syncer::SyncServiceObserver>
       sync_service_observer_;
 
-  // Used to listen for pref changes to allow / disallow deleting browsing data.
-  PrefChangeRegistrar profile_pref_registrar_;
-
   // Whether the sentence about other forms of history stored in user's account
   // should be displayed in the footer. This value is retrieved asynchronously,
   // so we cache it here.
   bool show_history_footer_;
 
   // Whether we should show a dialog informing the user about other forms of
   // history stored in their account after the history deletion is finished.
   bool show_history_deletion_dialog_;
 
   // A weak pointer factory for asynchronous calls referencing this class.
   base::WeakPtrFactory<ClearBrowsingDataHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ClearBrowsingDataHandler);
 };
 
 }  // namespace settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_SETTINGS_CLEAR_BROWSING_DATA_HANDLER_H_