[WebProfilerBundle] [FrameworkBundle] profile forward controller action

closes #14358

The `Symfony\Bundle\FrameworkBundle\Controller\Controller::forward()`
now passes request attributes to its sub request, so when the profiler
will profile the sub request it will add its token to its hold by
reference parent request attributes.

The profiler main profiler layout displays a shortcut to the forwarded
sub request profile which is actually responsible for returning the
present response.

The web debug toolbar shows a notifying icon, meaning a shortcut to a
forwarded profile is available in the toolbar request panel.

Author: HeahDude

DataCollector/RequestDataCollector.php

@@ -141,6 +141,18 @@ public function collect(Request $request, Response $response, \Exception $except
                 'status_text' => Response::$statusTexts[(int) $statusCode],
             ));
         }
+
+        if ($parentRequestAttributes = $request->attributes->get('_forwarded')) {
+            if ($parentRequestAttributes instanceof ParameterBag) {
+                $parentRequestAttributes->set('_forward_token', $response->headers->get('x-debug-token'));
+            }
+        }
+        if ($request->attributes->has('_forward_controller')) {
+            $this->data['forward'] = array(
+                'token' => $request->attributes->get('_forward_token'),
+                'controller' => $this->parseController($request->attributes->get('_forward_controller')),
+            );
+        }
     }
 
     public function getPathInfo()
@@ -274,9 +286,26 @@ public function getRedirect()
         return isset($this->data['redirect']) ? $this->data['redirect'] : false;
     }
 
+    /**
+     * Gets the parsed forward controller.
+     *
+     * @return array|bool An array with keys 'token' the forward profile token, and
+     *                    'controller' the parsed forward controller, false otherwise
+     */
+    public function getForward()
+    {
+        return isset($this->data['forward']) ? $this->data['forward'] : false;
+    }
+
     public function onKernelController(FilterControllerEvent $event)
     {
         $this->controllers[$event->getRequest()] = $event->getController();
+
+        if ($parentRequestAttributes = $event->getRequest()->attributes->get('_forwarded')) {
+            if ($parentRequestAttributes instanceof ParameterBag) {
+                $parentRequestAttributes->set('_forward_controller', $event->getController());
+            }
+        }
     }
 
     public static function getSubscribedEvents()