Allow framing 'self'

This is required by the pdf viewer, since the files app on master uses the AppFramework it had applied the more strict defaults which made it not work on master.

apps/files/controller/viewcontroller.php

@@ -23,6 +23,7 @@ namespace OCA\Files\Controller;
 
 use OC\AppFramework\Http\Request;
 use OCP\AppFramework\Controller;
+use OCP\AppFramework\Http\ContentSecurityPolicy;
 use OCP\AppFramework\Http\RedirectResponse;
 use OCP\AppFramework\Http\TemplateResponse;
 use OCP\IL10N;
@@ -215,10 +216,15 @@ class ViewController extends Controller {
 		$params['appContents'] = $contentItems;
 		$this->navigationManager->setActiveEntry('files_index');
 
-		return new TemplateResponse(
+		$response = new TemplateResponse(
 			$this->appName,
 			'index',
 			$params
 		);
+		$policy = new ContentSecurityPolicy();
+		$policy->addAllowedFrameDomain('\'self\'');
+		$response->setContentSecurityPolicy($policy);
+
+		return $response;
 	}
 }

apps/files/tests/controller/ViewControllerTest.php

@@ -245,6 +245,9 @@ class ViewControllerTest extends TestCase {
 				],
 			]
 		);
+		$policy = new Http\ContentSecurityPolicy();
+		$policy->addAllowedFrameDomain('\'self\'');
+		$expected->setContentSecurityPolicy($policy);
 		$this->assertEquals($expected, $this->viewController->index('MyDir', 'MyView'));
 	}
 }