refactor(drop-down, autocomplete): apply comments #3977

Author: Lipata

projects/igniteui-angular/src/lib/drop-down/drop-down.component.html

@@ -1,5 +1,10 @@
-<div [ngClass]="listClass()" igxToggle [style.width]="width"
-(onOpening)="onToggleOpening($event)" (onOpened)="onToggleOpened()" (onAppended)="onToggleContentAppended()"
+<div [ngClass]="{
+    'igx-drop-down__list': items.length > 0,
+    'igx-drop-down__list--empty': items.length === 0 }"
+[style.width]="width"
+igxToggle
+(onAppended)="onToggleContentAppended()"
+(onOpening)="onToggleOpening($event)" (onOpened)="onToggleOpened()"
 (onClosing)="onToggleClosing($event)" (onClosed)="onToggleClosed()">
     <div class="igx-drop-down__list-scroll" #scrollContainer [attr.id]="this.listId" role="listbox"
     [style.height]="height"

projects/igniteui-angular/src/lib/drop-down/drop-down.component.ts

@@ -524,13 +524,6 @@ export class IgxDropDownComponent extends IgxDropDownBaseDirective implements ID
         }
     }
 
-    /**
-     * @hidden @internal
-     */
-    public listClass() {
-        return this.items.length > 0 ? 'igx-drop-down__list' : 'igx-drop-down__list--empty';
-    }
-
     /**
      * Handles the `onSelection` emit and the drop down toggle when selection changes
      * @hidden