Remove .html extension from links

chrome/common/extensions/docs/templates/intros/ttsEngine.html

 <h2 id="overview">Overview</h2>
 
 <p>An extension can register itself as a speech engine. By doing so, it
 can intercept some or all calls to functions such as
 $(ref:tts.speak) and
 $(ref:tts.stop)
 and provide an alternate implementation.
 Extensions are free to use any available web technology
 to provide speech, including streaming audio from a server, HTML5 audio,
 Native Client, or Flash. An extension could even do something different
@@ skipping 20 matching lines @@
         "event_types": ["start", "marker", "end"]
       },
       {
         "voice_name": "Pat",
         "lang": "en-US",
         "event_types": ["end"]
       }
     ]
   },</b>
   "background": {
-    "page": "background.html",
+    "page": "background",
     "persistent": false
   }
 }
 </pre>
 
 <p>An extension can specify any number of voices.</p>
 
 <p>The <code>voice_name</code> parameter is required. The name should be
 descriptive enough that it identifies the name of the voice and the
 engine used. In the unlikely event that two extensions register voices
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 If your extension does not register listeners for both
 <code>onSpeak</code> and <code>onStop</code>, it will not intercept any
 speech calls, regardless of what is in the manifest.</p>
 
 <p>The decision of whether or not to send a given speech request to an
 extension is based solely on whether the extension supports the given voice
 parameters in its manifest and has registered listeners
 for <code>onSpeak</code> and <code>onStop</code>. In other words,
 there's no way for an extension to receive a speech request and
 dynamically decide whether to handle it.</p>