Add a policy to disable mounting of external storage.

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 657 matching lines @@
 
 #if defined(OS_CHROMEOS)
 extern const char kSignedSettingsCache[];
 extern const char kHardwareKeyboardLayout[];
 extern const char kCarrierDealPromoShown[];
 extern const char kShouldAutoEnroll[];
 extern const char kAutoEnrollmentPowerLimit[];
 extern const char kDeviceActivityTimes[];
 extern const char kDeviceLocation[];
 extern const char kSyncSpareBootstrapToken[];
+extern const char kExternalStorageDisabled[];
 #endif
 
 extern const char kClearPluginLSODataEnabled[];
 extern const char kPepperFlashSettingsEnabled[];
 extern const char kDiskCacheDir[];
 extern const char kDiskCacheSize[];
 extern const char kMediaCacheSize[];
 
 extern const char kChromeOsReleaseChannel[];
 
@@ skipping 60 matching lines @@
 extern const char kNetworkProfileWarningsLeft[];
 extern const char kNetworkProfileLastWarningTime[];
 
 #if defined(OS_MACOSX)
 extern const char kMacLeopardObsoleteInfobarLastShown[];
 #endif  // defined(OS_MACOSX)
 
 }  // namespace prefs
 
 #endif  // CHROME_COMMON_PREF_NAMES_H_