Filled out the manifest page. Transferred info from dev.chromium.org...

common/extensions/docs/static/npapi.html

+<div id="pageData-title" class="pageData">NPAPI Plugins</div>
+
+<p>
+Leveraging HTML and JavaScript
+makes developing new extensions really easy,
+but what if you have existing legacy or proprietary code
+that you want to reuse in your extension? 
+You can bundle an NPAPI plugin with your extension,
+allowing you to call into native binary code from JavaScript.
+</p>
+
+<h2>Details</h2>
+
+<p>
+How to develop an NPAPI plugin is outside the scope of this document.
+See <a href="https://developer.mozilla.org/en/Plugins">Mozilla's
+NPAPI plugin reference</a> for information on how to do that.
+</p>
+
+<p>
+Once you have an NPAPI plugin,
+follow these steps to get your extension using it.
+</p>
+
+<ol>
+  <li> 
+    Add a section to your extension's <code>manifest.json</code>
+    that describes where to find the plugin,
+    along with other properties about it:
+    
+<pre>{
+  "name": "My extension",
+  ...
+  "plugins": [
+    { "path": "content_plugin.dll", "public": true },
+    { "path": "extension_plugin.dll" }
+  ]
+}</pre>
+
+    <p>
+    The "path" property specifies the path to your plugin,
+    relative to the manifest file.
+    The "public" property specifies whether
+    your plugin can be accessed by regular web pages;
+    the default is false,
+    meaning only your extension can load the plugin.
+    </p>
+   </li>
+   
+   <li>
+     Create an HTML file that loads your plugin by mime-type.
+     Assuming your mime-type is "application/x-my-extension":
+
+<pre>
+&lt;embed type="application/x-my-extension" id="pluginId"></embed>
+&lt;script>
+  var plugin = document.getElementById("pluginId");
+  var result = plugin.myPluginMethod();  // call a method in your plugin
+  console.log("my plugin returned: " + result);
+&lt;/script></pre>
+
+     <p>
+     This can be inside a toolstrip, a background page,
+     or any other HTML page used by your extension.
+     If your plugin is "public",
+     you can even use a content script to programmatically
+     insert your plugin into a web page.
+     </p>