An input with data binding.
By default you can only get notified of changes to an input's value due to user input:
<input value="{{myValue::input}}">iron-input adds the bind-value property that mirrors the value property, and can be used
for two-way data binding. bind-value will notify if it is changed either by user input or by script.
<input is="iron-input" bind-value="{{myValue}}">