Adding `content_security_policy` to a few sample extensions.

chrome/common/extensions/docs/examples/extensions/news_a11y/feed.css

+/**
+ * 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.
+ */
+
+body {
+  font-family: helvetica, arial, sans-serif;
+  font-size: 12px;
+  overflow: hidden;
+}
+
+a {
+  color:#0000CC;
+  text-decoration: underline;
+  cursor: pointer;
+}
+
+.open_box {
+  display: block;
+  overflow: hidden;
+  margin-right: 4px;
+  margin-top: 2px;
+  height: 12px;
+  width: 12px;
+  float: left;
+  clear: left;
+  background-image: url(sprite_arrows.gif);
+  background-position: 0px -24px;
+  cursor: pointer;
+}
+
+.opened .open_box {
+  background-position:-12px -24px;
+}
+
+.item {
+  padding: 2px 0px;
+}
+
+.item_title {
+  display: block;
+  min-width: 300px;
+  padding-left: 15px;
+  cursor: pointer;
+}
+
+.item_desc {
+  min-width: 500px;
+  height: 0px;
+  display: block;
+  border: none;
+  padding: 0px;
+  margin: 0px;
+  -webkit-transition: height 0.2s ease-out;
+}
+
+#title {
+  display: block;
+  margin-left: auto;
+}
+
+.error {
+  white-space: nowrap;
+  color: red;
+}
+
+.more {
+  display: block;
+  text-align: right;
+  padding-top: 20px;
+  padding-right: 10px;
+  color: #88C;
+}