feat: Add a blocklyVariableField CSS class to variable fields (#8359)

core/field_variable.ts

@@ -22,6 +22,7 @@ import {
   MenuGenerator,
   MenuOption,
 } from './field_dropdown.js';
+import * as dom from './utils/dom.js';
 import * as fieldRegistry from './field_registry.js';
 import * as internalConstants from './internal_constants.js';
 import type {Menu} from './menu.js';
@@ -148,6 +149,11 @@ export class FieldVariable extends FieldDropdown {
     this.doValueUpdate_(variable.getId());
   }
 
+  override initView() {
+    super.initView();
+    dom.addClass(this.fieldGroup_!, 'blocklyVariableField');
+  }
+
   override shouldAddBorderRect_() {
     const block = this.getSourceBlock();
     if (!block) {