dynamicContentMacro iframes sometimes match the wrong media query

Issue Summary

Sometimes, the media queries within the dynamicContentMacro iframe is matched incorrectly, so that an iframe matches media queries of exactly 300px, even when the actual size is much larger.

Steps to Reproduce

1. Install any connect app that uses the dynamicContentMacro module.

1. Create a page

1. Insert one of the dynamicContentMacros

1. Make sure your browser is larger than 300px and reload the page

1. With the iframe selected, run:
   window.matchMedia("(max-width: 301px)").matches

1. This will sometimes return true, even when the screen is larger than 301px.

Expected Results

window.matchMedia("(max-width: 301px)").matches should always return false for screens larger than 300px.

Actual Results

It occasionally returns false.
 

Workaround

Reload the page