This ensures that a standard header is shown on the front page whenever
a header video is set without a header image if the video doesn't load,
e.g., on mobile sizes or if the JS doesn't fire.
This adds a new class, `.has-header-video` that is added whenever the
`wp-custom-header-video-loaded` event is fired, which is then used to style
the custom headers along with `.has-header-image` whenever a header image
is available. This also changes the class name on the custom header media
wrapping `div` from `.custom-header-image` to `.custom-header-media`.
Props laurelfulford, joemcgill.
Fixes#38995.
Built from https://develop.svn.wordpress.org/trunk@39413
git-svn-id: http://core.svn.wordpress.org/trunk@39353 1a063a9b-81f0-0310-95a4-ce76da25c4cd
IE9 doesn't understands `vh ` (vertical height) when inside of an `iframe`. Normally IE9 will understand `vh` as the vertical height relative to the viewport, but in an `iframe`, IE9 thinks the vertical height is relative to the size of the whole page. So this fixes that when the site is viewed in the Customizer preview – an `iframe`.
Props laurelfulford.
Fixes#38722.
Built from https://develop.svn.wordpress.org/trunk@39215
git-svn-id: http://core.svn.wordpress.org/trunk@39155 1a063a9b-81f0-0310-95a4-ce76da25c4cd
