Core: Align branches: remove an unused variable, add comments

Closes gh-2233

src/css/support.js

@@ -10,6 +10,7 @@ define([
 		container = document.createElement( "div" ),
 		div = document.createElement( "div" );
 
+	// Finish early in limited (non-browser) environments
 	if ( !div.style ) {
 		return;
 	}