Default Browser .plist location
You don't add yourself to this plist—OS X manages this itself. For example, download a new browser and copy it to the Applications folder. Without opening it once, OS X will add it to the list in System Preferences.

This is achieved with the following in the Info.plist in the app:

&lt;key&gt;CFBundleURLTypes&lt;/key&gt;
&lt;array&gt;
    &lt;dict&gt;
        &lt;key&gt;CFBundleURLName&lt;/key&gt;
        &lt;string&gt;http URL&lt;/string&gt;
        &lt;key&gt;CFBundleURLSchemes&lt;/key&gt;
        &lt;array&gt;
            &lt;string&gt;http&lt;/string&gt;
        &lt;/array&gt;
    &lt;/dict&gt;
    &lt;dict&gt;
        &lt;key&gt;CFBundleURLName&lt;/key&gt;
        &lt;string&gt;Secure http URL&lt;/string&gt;
        &lt;key&gt;CFBundleURLSchemes&lt;/key&gt;
        &lt;array&gt;
            &lt;string&gt;https&lt;/string&gt;
        &lt;/array&gt;
    &lt;/dict&gt;
&lt;/array&gt;