polymer-veiled and polymer-unveil classes. To veil (initially hide) an element either include thepolymer-veiled class on the element or add to the array: Polymer.veiledElements. This list includes body by default but that can be removed to prevent body from getting de-fuoc'd. Note: Polymer automatically unveils elements at WebComponentsReady time, but elements can be dynamically unveiled by (1) adding the polymer-veiled class to hide them and (2) when they are ready, calling Polymer.unveilElements().Polymer.register() (commit)lightdom attribute on <polymer-element> for producing light dom instead of shadow dom.