Add sanbdoxed_pages to allow extension/app pages to be served in a sandboxed, unique origin

chrome/common/extensions/extension_constants.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.
 
 #ifndef CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_
 #define CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_
 #pragma once
 
 #include <string>
 
@@ skipping 234 matching lines @@
   extern const char kAppStateNotInstalled[];
   extern const char kAppStateInstalled[];
   extern const char kAppStateDisabled[];
   extern const char kAppStateRunning[];
   extern const char kAppStateCannotRun[];
   extern const char kAppStateReadyToRun[];
 
   // Error indicating that the app notifications API is not accessible by split
   // mode extensions in incognito windows.
   extern const char kAppNotificationsIncognitoError[];
+
+  // CSP value that makes resources be sandboxed (served from an unique origin,
+  // top-level navigation and popups are disabled).
+  extern const char kSandboxedContentSecurityPolicy[];
 }  // extension_misc
 
 #endif  // CHROME_COMMON_EXTENSIONS_EXTENSION_CONSTANTS_H_