Change access mode of disk devices when mounting based on config.

chrome/browser/chromeos/preferences.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 "chrome/browser/chromeos/preferences.h"
 
 #include <vector>
 
 #include "ash/autoclick/autoclick_controller.h"
 #include "ash/common/accessibility_types.h"
@@ skipping 282 matching lines @@
       user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
 
   // Initially all existing users would see "What's new" for current version
   // after update.
   registry->RegisterStringPref(prefs::kChromeOSReleaseNotesVersion,
                                "0.0.0.0",
                                user_prefs::PrefRegistrySyncable::SYNCABLE_PREF);
 
   registry->RegisterBooleanPref(prefs::kExternalStorageDisabled, false);
 
+  registry->RegisterBooleanPref(prefs::kExternalStorageReadOnly, false);
+
   registry->RegisterStringPref(prefs::kTermsOfServiceURL, "");
 
   registry->RegisterBooleanPref(prefs::kTouchHudProjectionEnabled, false);
 
   registry->RegisterBooleanPref(prefs::kTouchVirtualKeyboardEnabled, false);
 
   input_method::InputMethodSyncer::RegisterProfilePrefs(registry);
 
   registry->RegisterBooleanPref(
       prefs::kResolveTimezoneByGeolocation, true,
@@ skipping 464 matching lines @@
   touch_hud_projection_enabled_.SetValue(enabled);
 }
 
 void Preferences::ActiveUserChanged(const user_manager::User* active_user) {
   if (active_user != user_)
     return;
   ApplyPreferences(REASON_ACTIVE_USER_CHANGED, "");
 }
 
 }  // namespace chromeos