Issue #3315490 by alexpott, Wim Leers: Random fail in...

Issue #3315490 by alexpott, Wim Leers: Random fail in Drupal\Tests\layout_builder\FunctionalJavascript\InlineBlockPrivateFilesTest

(cherry picked from commit 7690a8e6)

core/modules/layout_builder/tests/src/FunctionalJavascript/InlineBlockPrivateFilesTest.php

@@ -171,9 +171,9 @@ protected function replaceFileInBlock(FileInterface $file) {
     $assert_session = $this->assertSession();
     $page = $this->getSession()->getPage();
     $this->clickContextualLink(static::INLINE_BLOCK_LOCATOR, 'Configure');
+    $assert_session->waitForElement('css', "#drupal-off-canvas input[value='Remove']");
     $assert_session->assertWaitOnAjaxRequest();
-    $page->pressButton('Remove');
-    $assert_session->assertWaitOnAjaxRequest();
+    $page->find('css', '#drupal-off-canvas')->pressButton('Remove');
     $this->attachFileToBlockForm($file);
     $page->pressButton('Update');
     $this->assertDialogClosedAndTextVisible($file->label(), static::INLINE_BLOCK_LOCATOR);
@@ -269,6 +269,7 @@ protected function getFileSecret(FileInterface $file) {
   protected function attachFileToBlockForm(FileInterface $file) {
     $assert_session = $this->assertSession();
     $page = $this->getSession()->getPage();
+    $this->assertSession()->waitForElementVisible('named', ['field', 'files[settings_block_form_field_file_0]']);
     $page->attachFileToField("files[settings_block_form_field_file_0]", $this->fileSystem->realpath($file->getFileUri()));
     $assert_session->assertWaitOnAjaxRequest();
     $this->assertNotEmpty($assert_session->waitForLink($file->label()));