Merge branch '2.8' into 3.0

* 2.8:
  [HttpKernel] fixed internal subrequests having an if-modified-since-header
  [Security] Fix deprecated usage of DigestAuthenticationEntryPoint::getKey() in DigestAuthenticationListener
  [Validator] Added additional MasterCard range to the CardSchemeValidator
  Make the exception message more clear.
  [Form] fixed bug - name in ButtonBuilder
  [DoctrineBridge] added missing error code for constraint.
  [ClassLoader] Fix declared classes being computed when not needed
  [varDumper] Fix missing usage of ExceptionCaster::$traceArgs

Conflicts:
	src/Symfony/Bridge/Doctrine/Validator/Constraints/UniqueEntityValidator.php
	src/Symfony/Component/ClassLoader/ClassCollectionLoader.php

ClassCollectionLoader.php

@@ -43,9 +43,9 @@ class ClassCollectionLoader
 
         self::$loaded[$name] = true;
 
-        $declared = array_merge(get_declared_classes(), get_declared_interfaces(), get_declared_traits());
-
         if ($adaptive) {
+            $declared = array_merge(get_declared_classes(), get_declared_interfaces(), get_declared_traits());
+
             // don't include already declared classes
             $classes = array_diff($classes, $declared);
 
@@ -84,11 +84,14 @@ class ClassCollectionLoader
             }
         }
 
-        if (!$reload && is_file($cache)) {
+        if (!$reload && file_exists($cache)) {
             require_once $cache;
 
             return;
         }
+        if (!$adaptive) {
+            $declared = array_merge(get_declared_classes(), get_declared_interfaces(), get_declared_traits());
+        }
 
         $files = array();
         $content = '';