Support: ensure display is set to block for the support div (#4844)

- Fixes an issue with the support test in iframes in Android 8 Chrome 86+,
  where display: inline resulted in unexpected height values.

Fixes gh-4832

src/css/support.js

@@ -122,6 +122,14 @@ define( [
 				tr.style.height = "1px";
 				trChild.style.height = "9px";
 
+				// Support: Android 8 Chrome 86+
+				// In our bodyBackground.html iframe,
+				// display for all div elements is set to "inline",
+				// which causes a problem only in Android 8 Chrome 86.
+				// Ensuring the div is display: block
+				// gets around this issue.
+				trChild.style.display = "block";
+
 				documentElement
 					.appendChild( table )
 					.appendChild( tr )