Add a policy and pref to control whether deleting browsing and download history is allowed.

chrome/common/pref_names.h

 // 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.
 
 // Constants for the names of various preferences, for easier changing.
 
 #ifndef CHROME_COMMON_PREF_NAMES_H_
 #define CHROME_COMMON_PREF_NAMES_H_
 
 #include <stddef.h>
@@ skipping 306 matching lines @@
 extern const char kDeletePasswords[];
 extern const char kDeleteFormData[];
 extern const char kDeleteHostedAppsData[];
 extern const char kDeauthorizeContentLicenses[];
 extern const char kEnableContinuousSpellcheck[];
 extern const char kSpeechRecognitionFilterProfanities[];
 extern const char kSpeechRecognitionTrayNotificationShownContexts[];
 extern const char kEnabledLabsExperiments[];
 extern const char kEnableAutoSpellCorrect[];
 extern const char kSavingBrowserHistoryDisabled[];
+extern const char kAllowDeletingBrowserHistory[];
 extern const char kForceSafeSearch[];
 extern const char kDeleteTimePeriod[];
 extern const char kLastClearBrowsingDataTime[];
 #if defined(TOOLKIT_GTK)
 extern const char kUsesSystemTheme[];
 #endif
 extern const char kCurrentThemePackFilename[];
 extern const char kCurrentThemeID[];
 extern const char kCurrentThemeImages[];
 extern const char kCurrentThemeColors[];
@@ skipping 508 matching lines @@
 extern const char kRLZDisabled[];
 #endif
 
 #if defined(ENABLE_APP_LIST)
 extern const char kAppListProfile[];
 #endif
 
 }  // namespace prefs
 
 #endif  // CHROME_COMMON_PREF_NAMES_H_