Wordpress - WP function/filter for modifying http headers?

Here is the code I've used, based on the original question and on Dominic P's answer...

/*
 * Modify HTTP header
 */
function add_header_xua($headers) {

    // var_dump($headers); #=> if you want to see the current headers...  

    if (!is_admin()) {
        $headers['X-UA-Compatible'] = 'IE=edge,chrome=1';    
    }

    return $headers;     
}
add_filter('wp_headers', 'add_header_xua');

Once you've added that code to your functions.php file, you can check it works by running a test at http://web-sniffer.net/ to ensure the HTTP headers have indeed changed.

I know it's been a while, but if anyone else stumbles on this, I found a WordPress hook specifically for modifying HTTP headers. The hook is wp_headers and it's called in the wp class.

The first argument passed is an array of headers with the header name as the key. The second argument is a reference to the wp class object.

The init action is the wrong place to do it. A better place would be at template_redirect, so that you only affect the front end view of the site and not the admin areas.