minor #21346 [DependencyInjection] Add some missing typehints in YamlFileLoader (dunglas)

This PR was merged into the 2.7 branch.

Discussion
----------

[DependencyInjection] Add some missing typehints in YamlFileLoader

| Q             | A
| ------------- | ---
| Branch?       | 2.7
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | n/a
| License       | MIT
| Doc PR        | n/a

Commits
-------

34330e5136 [DependencyInjection] Add some missing typehints in YamlFileLoader

Author: fabpot

Loader/YamlFileLoader.php

@@ -85,7 +85,7 @@ public function supports($resource, $type = null)
      * @param array  $content
      * @param string $file
      */
-    private function parseImports($content, $file)
+    private function parseImports(array $content, $file)
     {
         if (!isset($content['imports'])) {
             return;
@@ -112,7 +112,7 @@ private function parseImports($content, $file)
      * @param array  $content
      * @param string $file
      */
-    private function parseDefinitions($content, $file)
+    private function parseDefinitions(array $content, $file)
     {
         if (!isset($content['services'])) {
             return;
@@ -420,7 +420,7 @@ private function resolveServices($value)
      *
      * @param array $content
      */
-    private function loadFromExtensions($content)
+    private function loadFromExtensions(array $content)
     {
         foreach ($content as $namespace => $values) {
             if (in_array($namespace, array('imports', 'parameters', 'services'))) {