Issue #2646280 by Elijah Lynn: Remove IE pre-check and post-check Cache-control headers

core/includes/install.core.inc

@@ -993,7 +993,7 @@ function install_display_output($output, $install_state) {
   $default_headers = array(
     'Expires' => 'Sun, 19 Nov 1978 05:00:00 GMT',
     'Last-Modified' => gmdate(DATE_RFC1123, REQUEST_TIME),
-    'Cache-Control' => 'no-cache, must-revalidate, post-check=0, pre-check=0',
+    'Cache-Control' => 'no-cache, must-revalidate',
     'ETag' => '"' . REQUEST_TIME . '"',
   );
   $response->headers->add($default_headers);

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

@@ -263,7 +263,7 @@ protected function setResponseCacheable(Response $response, Request $request) {
    *   A response object.
    */
   protected function setCacheControlNoCache(Response $response) {
-    $response->headers->set('Cache-Control', 'no-cache, must-revalidate, post-check=0, pre-check=0');
+    $response->headers->set('Cache-Control', 'no-cache, must-revalidate');
   }
 
   /**

core/modules/page_cache/src/Tests/PageCacheTest.php

@@ -263,7 +263,7 @@ function testPageCache() {
     $this->drupalGet('system-test/set-header', array('query' => array('name' => 'Foo', 'value' => 'bar')));
     $this->assertFalse($this->drupalGetHeader('X-Drupal-Cache'), 'Caching was bypassed.');
     $this->assertTrue(strpos(strtolower($this->drupalGetHeader('Vary')), 'cookie') === FALSE, 'Vary: Cookie header was not sent.');
-    $this->assertEqual($this->drupalGetHeader('Cache-Control'), 'must-revalidate, no-cache, post-check=0, pre-check=0, private', 'Cache-Control header was sent.');
+    $this->assertEqual($this->drupalGetHeader('Cache-Control'), 'must-revalidate, no-cache, private', 'Cache-Control header was sent.');
     $this->assertEqual($this->drupalGetHeader('Expires'), 'Sun, 19 Nov 1978 05:00:00 GMT', 'Expires header was sent.');
     $this->assertEqual($this->drupalGetHeader('Foo'), 'bar', 'Custom header was sent.');
 
@@ -452,12 +452,12 @@ public function testCacheableResponseResponses() {
     // GET a URL, which would be marked as a cache miss if it were cacheable.
     $this->drupalGet('/system-test/respond-reponse');
     $this->assertFalse($this->drupalGetHeader('X-Drupal-Cache'), 'Drupal page cache header not found.');
-    $this->assertEqual($this->drupalGetHeader('Cache-Control'), 'must-revalidate, no-cache, post-check=0, pre-check=0, private', 'Cache-Control header was sent');
+    $this->assertEqual($this->drupalGetHeader('Cache-Control'), 'must-revalidate, no-cache, private', 'Cache-Control header was sent');
 
     // GET it again, verify it's still not cached.
     $this->drupalGet('/system-test/respond-reponse');
     $this->assertFalse($this->drupalGetHeader('X-Drupal-Cache'), 'Drupal page cache header not found.');
-    $this->assertEqual($this->drupalGetHeader('Cache-Control'), 'must-revalidate, no-cache, post-check=0, pre-check=0, private', 'Cache-Control header was sent');
+    $this->assertEqual($this->drupalGetHeader('Cache-Control'), 'must-revalidate, no-cache, private', 'Cache-Control header was sent');
 
     // GET a URL, which would be marked as a cache miss if it were cacheable.
     $this->drupalGet('/system-test/respond-public-response');