Issue #3214211 by gapple, longwave: Stop setting X-UA-Compatible header

core/lib/Drupal/Core/EventSubscriber/FinishResponseSubscriber.php

@@ -117,10 +117,6 @@ public function onRespond(ResponseEvent $event) {
     $request = $event->getRequest();
     $response = $event->getResponse();
 
-    // Set the X-UA-Compatible HTTP header to force IE to use the most recent
-    // rendering engine.
-    $response->headers->set('X-UA-Compatible', 'IE=edge', FALSE);
-
     // Set the Content-language header.
     $response->headers->set('Content-language', $this->languageManager->getCurrentLanguage()->getId());
 

core/modules/system/tests/src/Functional/Routing/RouterTest.php

@@ -42,7 +42,6 @@ public function testFinishResponseSubscriber() {
     $session = $this->getSession();
 
     // Check expected headers from FinishResponseSubscriber.
-    $this->assertSession()->responseHeaderEquals('X-UA-Compatible', 'IE=edge');
     $this->assertSession()->responseHeaderEquals('Content-language', 'en');
     $this->assertSession()->responseHeaderEquals('X-Content-Type-Options', 'nosniff');
     $this->assertSession()->responseHeaderEquals('X-Frame-Options', 'SAMEORIGIN');