This add-on uses names that are sure to create a conflict if anybody else chooses to name their add-on and widgetset without including the add-on’s name in the package.
The widget class is:
org.vaadin.addons.ResetButtonForTextField.java
and widgetset is named just:
org.vaadin.addons.WidgetSet.gwt.xml
Less conflict-prone names would be more like:
org.vaadin.addons.resetbuttonvaadin8.ResetButtonForTextField.java
org.vaadin.addons.resetbuttonvaadin8.WidgetSet.gwt.xml