bug #4048 $this->request replaced by $request (danielsan)

This PR was submitted for the 2.5 branch but it was merged into the 2.3 branch instead (closes #4048).

Discussion
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$this->request replaced by $request

Using $this->request it does not work
one the $request is being injected

Commits
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b9b4e09 $this->request replaced by $request

quick_tour/the_controller.rst

@@ -148,7 +148,7 @@ from any controller::
 
     public function indexAction(Request $request)
     {
-        $session = $this->request->getSession();
+        $session = $request->getSession();
 
         // store an attribute for reuse during a later user request
         $session->set('foo', 'bar');