fix(item): only add .item-button class

ionic/components/button/button.ts

@@ -92,6 +92,13 @@ export class Button {
     }
   }
 
+  /**
+   * @private
+   */
+  addClass(className) {
+    this._renderer.setElementClass(this._elementRef, className, true);
+  }
+
   /**
    * @private
    */

ionic/components/item/item.ts

@@ -64,7 +64,9 @@ export class Item {
 
   @ContentChildren(Button)
   set _buttons(buttons) {
-    Button.setRoles(buttons, 'item-button');
+    buttons.toArray().forEach(button => {
+      button.addClass('item-button');
+    });
   }
 
   @ContentChildren(Icon)