annotations - allow for pointer events to be controlled on the slotted element (#1020)
annotations - allow for pointer events to be controlled on the slotted element (#1020)

* annotations - allow for pointer events to be controlled on the slotted element

(cherry picked from commit b3dc61841b2ce6f782476446764ca8ec6ec91ba2)

* annotations slotted elements default to pointer-events: initial

PolymerLabs/model-viewer,google/model-viewer,PolymerLabs/model-viewer,google/model-viewer,google/model-viewer,google/model-viewer