Database bootstrap level before booting kernel.

Switching to the test database connection only happens when
_drupal_bootstrap_database() runs before executing a first query.

To avoid complicating the boostrap with more fine grained level booting, just
boot the DrupalKernel after DRUPAL_BOOTSTRAP_CODE. Getting rid of those levels
is for a seperate issue.

Additionally mirror the changes in the testing files
core/modules/system/tests/http.php and https.php.

core/lib/Drupal/Core/DrupalKernel.php

@@ -23,14 +23,8 @@ public function registerBundles() {
       new CoreBundle(),
     );
 
-    // Rather than bootstrapping to a higher phase prior to booting the Kernel, which
-    // would ensure these files are loaded already, we want to boot the Kernel as
-    // early as possible in the bootstrapping phase.
     // TODO: Somehow remove the necessity of calling system_list() to find out which
     // bundles exist.
-    require_once DRUPAL_ROOT . '/core/includes/cache.inc';
-    require_once DRUPAL_ROOT . '/core/includes/module.inc';
-    require_once DRUPAL_ROOT . '/core/includes/database.inc';
 
     $modules = array_keys(system_list('module_enabled'));
     foreach ($modules as $module) {

core/modules/system/tests/http.php

@@ -5,6 +5,7 @@
  * Fake an HTTP request, for use during testing.
  */
 
+use Drupal\Core\DrupalKernel;
 use Symfony\Component\HttpFoundation\Request;
 
 // Set a global variable to indicate a mock HTTP request.
@@ -36,6 +37,7 @@
 
 drupal_bootstrap(DRUPAL_BOOTSTRAP_CODE);
 
-$kernel = drupal_container()->get('httpkernel');
+$kernel = new DrupalKernel('prod', FALSE);
+$kernel->boot();
 $response = $kernel->handle($request)->prepare($request)->send();
 $kernel->terminate($request, $response);

core/modules/system/tests/https.php

@@ -5,6 +5,7 @@
  * Fake an https request, for use during testing.
  */
 
+use Drupal\Core\DrupalKernel;
 use Symfony\Component\HttpFoundation\Request;
 
 // Set a global variable to indicate a mock HTTPS request.
@@ -35,6 +36,7 @@
 
 drupal_bootstrap(DRUPAL_BOOTSTRAP_CODE);
 
-$kernel = drupal_container()->get('httpkernel');
+$kernel = new DrupalKernel('prod', FALSE);
+$kernel->boot();
 $response = $kernel->handle($request)->prepare($request)->send();
 $kernel->terminate($request, $response);

index.php

@@ -30,9 +30,6 @@
 // container at some point.
 request($request);
 
-$kernel = new DrupalKernel('prod', FALSE);
-$kernel->boot();
-
 // Bootstrap all of Drupal's subsystems, but do not initialize anything that
 // depends on the fully resolved Drupal path, because path resolution happens
 // during the REQUEST event of the kernel.
@@ -40,6 +37,9 @@
 // @see Drupal\Core\EventSubscriber\LegacyRequestSubscriber;
 drupal_bootstrap(DRUPAL_BOOTSTRAP_CODE);
 
+$kernel = new DrupalKernel('prod', FALSE);
+$kernel->boot();
+
 $response = $kernel->handle($request)->prepare($request)->send();
 
 $kernel->terminate($request, $response);