test: update app-layout visual tests to use fixed height

Author: web-padawan

packages/app-layout/test/visual/fixed-height-styles.js

@@ -0,0 +1,12 @@
+import { css, registerStyles } from '@vaadin/vaadin-themable-mixin/vaadin-themable-mixin.js';
+
+registerStyles(
+  'vaadin-app-layout',
+  css`
+    :host,
+    :host([overlay]) [part='backdrop'],
+    [part='drawer'] {
+      height: inherit;
+    }
+  `,
+);

packages/app-layout/test/visual/lumo/app-layout.test.js

@@ -1,5 +1,6 @@
 import { fixtureSync } from '@vaadin/testing-helpers/dist/fixture.js';
 import { visualDiff } from '@web/test-runner-visual-regression';
+import '../fixed-height-styles.js';
 import '../../../theme/lumo/vaadin-app-layout.js';
 import '../../../theme/lumo/vaadin-drawer-toggle.js';
 
@@ -8,7 +9,7 @@ describe('app-layout', () => {
 
   beforeEach(() => {
     div = document.createElement('div');
-    div.style.height = '100%';
+    div.style.height = '600px';
 
     element = fixtureSync(
       `