[Form] Add phpdoc to `RequestHandlerInterface::isFileUpload()` method

src/Symfony/Component/Form/Extension/HttpFoundation/HttpFoundationRequestHandler.php

@@ -108,6 +108,9 @@ class HttpFoundationRequestHandler implements RequestHandlerInterface
         $form->submit($data, 'PATCH' !== $method);
     }
 
+    /**
+     * {@inheritdoc}
+     */
     public function isFileUpload($data)
     {
         return $data instanceof File;

src/Symfony/Component/Form/NativeRequestHandler.php

@@ -118,6 +118,9 @@ class NativeRequestHandler implements RequestHandlerInterface
         $form->submit($data, 'PATCH' !== $method);
     }
 
+    /**
+     * {@inheritdoc}
+     */
     public function isFileUpload($data)
     {
         // POST data will always be strings or arrays of strings. Thus, we can be sure

src/Symfony/Component/Form/RequestHandlerInterface.php

@@ -27,7 +27,9 @@ interface RequestHandlerInterface
     public function handleRequest(FormInterface $form, $request = null);
 
     /**
-     * @param mixed $data
+     * Returns true if the given data is a file upload.
+     *
+     * @param mixed $data The form field data
      *
      * @return bool
      */