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

Finder.php

@@ -297,6 +297,10 @@ public function size($size)
     /**
      * Excludes directories.
      *
+     * Directories passed as argument must be relative to the ones defined with the `in()` method. For example:
+     *
+     *     $finder->in(__DIR__)->exclude('ruby');
+     *
      * @param string|array $dirs A directory path or an array of directories
      *
      * @return $this