Whitelisting `127.0.0.1` and `localhost` for HTTP in extensions' CSP.

chrome/common/extensions/docs/server2/templates/articles/contentSecurityPolicy.html

 <h1>Content Security Policy (CSP)</h1>
 
 
 <p>
   In order to mitigate a large class of potental cross-site scripting issues,
   Chrome's extension system has incorporated the general concept of
   <a href="http://dvcs.w3.org/hg/content-security-policy/raw-file/tip/csp-specification.dev.html">
     <strong>Content Security Policy (CSP)</strong>
   </a>. This introduces some fairly strict policies that will make extensions
   more secure by default, and provides you with the ability to create and
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   exactly the resources you expect, and haven't been replaced by an active
   network attacker. As <a
   href="http://en.wikipedia.org/wiki/Man-in-the-middle_attack">man-in-the-middle
   attacks</a> are both trivial and undetectable over HTTP, those origins will
   not be accepted. Currently, we allow whitelisting origins with the following
   schemes: <code>HTTPS</code>, <code>chrome-extension</code>, and
   <code>chrome-extension-resource</code>.
 </p>
 
 <p>
+  To ease development, we're also allowing the whitelisting of resources loaded
+  over HTTP from servers on your local machine. You may whitelist script and
+  object sources on any port of either <code>http://127.0.0.1</code> or
+  <code>http://localhost</code>.
+</p>
+
+<p>
   A relaxed policy definition which allows script resources to be loaded from
   <code>example.com</code> over HTTPS might look like:
 </p>
 
 <pre>{
   ...,
   "content_security_policy": "script-src 'self' https://example.com; object-src 'self'",
   ...
 }</pre>
 
@@ skipping 15 matching lines @@
 
 <p>
   You may, of course, tighten this policy to whatever extent your extension
   allows in order to increase security at the expense of convenience. To specify
   that your extension can only load resources of <em>any</em> type (images, etc)
   from its own package, for example, a policy of <code>default-src 'self'</code>
   would be appropriate. The <a href="samples.html#mappy">Mappy</a> sample
   extension is a good example of an extension that's been locked down above and
   beyond the defaults.
 </p>