Adding `content_security_policy` to a few sample extensions.

chrome/common/extensions/docs/examples/api/extension/isAllowedAccess/popup.js

+// Copyright (c) 2011 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.
+
+chrome.extension.isAllowedFileSchemeAccess(function(state) {
+  var el = document.getElementById('file');
+  el.textContent = el.className = state ? 'true': 'false';
+});
+chrome.extension.isAllowedIncognitoAccess(function(state) {
+  var el = document.getElementById('incognito');
+  el.textContent = el.className = state ? 'true': 'false';
+});