Merge branch '4.0'

* 4.0:
  fix the handling of timestamp in the MongoDBSessionHandler
  Improve the documentation of `Finder::exclude()`
  [DI] Skip resource tracking if disabled
  [WebProfilerBundle] fix wrong variable for profiler counting ajax requests

Author: fabpot

ContainerBuilder.php

@@ -326,9 +326,11 @@ public function getReflectionClass(?string $class, bool $throw = true): ?\Reflec
         try {
             if (isset($this->classReflectors[$class])) {
                 $classReflector = $this->classReflectors[$class];
-            } else {
+            } elseif ($this->trackResources) {
                 $resource = new ClassExistenceResource($class, false);
                 $classReflector = $resource->isFresh(0) ? false : new \ReflectionClass($class);
+            } else {
+                $classReflector = new \ReflectionClass($class);
             }
         } catch (\ReflectionException $e) {
             if ($throw) {