Give up entirely on firefox' stupid 'smart' scrollbars

YOU WANNA NOT MATCH THE CONTENT IN THE NAME OF MATCHING THE CONTENT,
FINE. I WON'T STOP YOU. FECKING AAAAARGH.

Because just feckin' matching the interface theme for top-level ones
would have made waaaaay too much sense... or, I dunno, taking the
average of *visible* backgrounds on the page to see if it's overall
light or dark...

But nope. Let's just use the body background, which is usually
entirely covered up anyway. How could that possibly go wrong?!

Change-Id: Ib31030815c947622aaad6340fbafbd6103fef21f

resources/screen-common.less

@@ -11,16 +11,13 @@ body {
 body {
 	font-family: @fonts;
 	color: @text;
-	/* Make firefox's 'smart' scrollbars actually match the content */
-	background: @base100;
+	// Footer colour; results in a weird distracting dark scrollbar in firefox, but fuck firefox
+	// Setting it here avoids a jump to white after the footer, which is even more distracting
+	background: @base30;
 	font-size: @font-size;
 	line-height: 1.5;
 }
 
-#mw-wrapper {
-	background: @base30;
-}
-
 #mw-content {
 	.box;
 	background: @background;