This diff handles correctly measuring multimedia messages. Multimedia needed to be handled a little bit differently since we use the image height and the composed message width to determine the contentHeight and we actually don't perform a measurement on multimedia messages.
This means that for multimedia messages we only need to measure the inline engagement and then in multimediaMessageItemHeight we can add the contentHeight w/ the height of the inline engagement we get from the NodeHeightMeasurer.
Depends on D8632