This is a variation of what I use to force ie to edge on a drupal site. I use it in Codit module. https://www.drupal.org/project/codit

gistfile1.php

/**
 * Implements hook_init().
 */
function mymodule_init() {
  // This is called on every page request (cached and non-cached).
  mymodule_set_ie_to_edge();

}



/**
 * Set the header to force IE to edge mode (the highest level of IE installed).
 */
function mymodule_set_ie_to_edge() {

  // Force ie to not use compatibility mode.
  if (!empty($_GET) && !empty($_GET['debug']) && ($_GET['debug'] == 'ie')) {
    // There is a debug so do not force to use edge, do nothing.
  }
  else {
    // There is no debugging going on, so force ie to use edge.
    header('X-UA-Compatible: IE=edge');
    // Send X-UA-Compatible HTTP header to force IE to use the most recent
    // rendering engine or use Chrome's frame rendering engine if available.
    // It is not possible to use drupal_add_http_header() as Drupal 7 does not
    // store HTTP headers in the page cache.
    $element = array(
      '#tag' => 'meta',
      '#attributes' => array(
        'http-equiv' => 'X-UA-Compatible',
        'content' => 'IE=edge',
      ),
    );
    // This element has no effect on forcing edge, but is a visual indicator in the 
    // html head of what is happening.
    drupal_add_html_head($element, 'x_ua_compatible');
  }
}