Materialized font style for TrayItemMore type system tray rows.

ash/common/system/tray/tray_popup_item_style_observer.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_COMMON_SYSTEM_TRAY_TRAY_POPUP_ITEM_STYLE_OBSERVER_H_
+#define ASH_COMMON_SYSTEM_TRAY_TRAY_POPUP_ITEM_STYLE_OBSERVER_H_
+
+namespace ash {
+
+class TrayPopupItemStyleObserver {
+ public:
+  // Notified by TrayPopupItemStyle instances when the Style is updated (even if
+  // the style values aren't changing).
+  virtual void OnTrayPopupItemStyleUpdated() = 0;
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_SYSTEM_TRAY_TRAY_POPUP_ITEM_STYLE_OBSERVER_H_