README.md

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_[Demo and API docs](https://elements.polymer-project.org/elements/iron-checked-element-behavior)_


##Polymer.IronCheckedElementBehavior

Use `Polymer.IronCheckedElementBehavior` to implement a custom element
that has a `checked` property, which can be used for validation if the
element is also `required`. Element instances implementing this behavior
will also be registered for use in an `iron-form` element.