Adding `content_security_policy` to a few sample extensions.

chrome/common/extensions/docs/examples/api/browserAction/set_icon_path/background.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.
+
+var min = 1;
+var max = 5;
+var current = min;
+
+function updateIcon() {
+  chrome.browserAction.setIcon({path:"icon" + current + ".png"});
+  current++;
+
+  if (current > max)
+    current = min;
+}
+
+chrome.browserAction.onClicked.addListener(updateIcon);
+updateIcon();