Have way to specify unknown size in the spec

[ryanthompson591]

Sometimes on initialization of a preroll the size of the video might not yet be known.

In this case it would be useful in the spec to have a way to let the ad know that the dimensions are not yet known.

Proposal: Dimensions may use -1 to specify when something is unknown.

For example

videoDimensions: { x: 0, y: 0, width: -1, height: -1, }

would indicate that the video will be in the top left corner but the width and height are not yet known.

[mimidden]

Committee accepts this.