Adding `content_security_policy` to imageinfo extension.

chrome/common/extensions/docs/examples/extensions/imageinfo/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.
+
+/**
+ * Returns a handler which will open a new window when activated.
+ */
+function getClickHandler() {
+  return function(info, tab) {
+
+    // The srcUrl property is only available for image elements.
+    var url = 'info.html#' + info.srcUrl;
+
+    // Create a new window to the info page.
+    chrome.windows.create({ url: url, width: 520, height: 660 });
+  };
+};
+
+/**
+ * Create a context menu which will only show up for images.
+ */
+chrome.contextMenus.create({
+  "title" : "Get image info",
+  "type" : "normal",
+  "contexts" : ["image"],
+  "onclick" : getClickHandler()
+});