Replace the existing hook_init with something like this... unless the existing init has other stuff in it. Then just move these items out.

gistfile1.txt

/**
 * Implements hook_boot().
 */
function local_framework_boot() {
  // Set http header to force ie to edge mode to prevent compatibility-mode.
  // This is the default behaviour.  On all but prod set doj_theme_ie_to_edge=0.
  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.
    // 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.
    header('X-UA-Compatible: IE=edge');
  }
}

/**
 * Implements hook_preprocess_page().
 */
function local_framework_preprocess_page(&$variables) {
  // Set http header to force ie to edge mode to prevent compatibility-mode.
  if (!empty($_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, set the meta tag for edge.
    $element = array(
      '#tag' => 'meta',
      '#attributes' => array(
        'http-equiv' => 'X-UA-Compatible',
        'content' => 'IE=edge',
      ),
    );
    // This element has no effect on forcing edge, but is a visual indicator in
    // the html head of what is happening. If it is present, so is the header.
    drupal_add_html_head($element, 'x_ua_compatible');
  }
}