Jetpack Infinite Scroll Breaks Video Shortcode Display Sizing

#### Steps to reproduce the issue
Enable infinite scroll in Jetpack, video embeds using Wordpress video shortcode do not responsively resize but appear to display in full content width (i.e, the content_width global value). Reproduced with multiple themes including twenty seventeen.

#### What I expected
Video should resize according to typical responsive design behavior.

#### What happened instead
Video overflows container.

Start by reproducing the issue with Jetpack infinite scroll enabled and a WordPress video shortcode, including the Twenty Seventeen theme. Trace the video sizing behavior during infinite-scroll loading; done means the video remains responsive within its content container without overflowing.

Written by the indexing model from the issue text.