Update references to the extension messaging APIs to point to the "runtime"

chrome/common/extensions/docs/templates/articles/content_scripts.html

 <h1>Content Scripts</h1>
 
 
 <p>
 Content scripts are JavaScript files that run in the context of web pages.
 By using the standard
 <a href="http://www.w3.org/TR/DOM-Level-2-HTML/">Document
 Object Model</a> (DOM),
 they can read details of the web pages the browser visits,
 or make changes to them.
@@ skipping 324 matching lines @@
 
 <p>Another important benefit of isolated worlds is that they completely separate the JavaScript on the page from the JavaScript in extensions. This allows us to offer extra functionality to content scripts that should not be accessible from web pages without worrying about web pages accessing it.
 
 
 <h2 id="host-page-communication">Communication with the embedding page</h2>
 
 <p>Although the execution environments of content scripts and the pages that host them are isolated from each other, they share access to the page's DOM. If the page wishes to communicate with the content script (or with the extension via the content script), it must do so through the shared DOM.</p>
 <p>An example can be accomplished using window.postMessage (or window.webkitPostMessage for Transferable objects):</p>
 <pre>contentscript.js
 ================
-var port = chrome.extension.connect();
+var port = chrome.runtime.connect();
 
 window.addEventListener("message", function(event) {
     // We only accept messages from ourselves
     if (event.source != window)
       return;
 
     if (event.data.type &amp;&amp; (event.data.type == "FROM_PAGE")) {
       console.log("Content script received: " + event.data.text);
       port.postMessage(event.data.text);
     }
@@ skipping 96 matching lines @@
 
 <p>
 The next video describes message passing,
 featuring an example of a content script
 sending a request to its parent extension.
 </p>
 
 <p>
 <iframe title="YouTube video player" width="640" height="390" src="http://www.youtube.com/embed/B4M_a7xejYI?rel=0" frameborder="0" allowfullscreen></iframe>
 </p>