Add 'webkit' CSS class to document when WebKit engine is detected.

src/General/Main.coffee

@@ -126,7 +126,7 @@ Main =
     $('link[href*=mobile]', d.head)?.disabled = true
     $.addClass doc, 'fourchan-x', 'seaweedchan'
     $.addClass doc, if g.VIEW is 'thread' then 'thread-view' else g.VIEW
-    $.addClass doc, if chrome? then 'blink' else 'gecko'
+    $.addClass doc, $.engine if $.engine
     $.addStyle Main.css, 'fourchanx-css'
 
     keyboard = false

src/General/lib/$.coffee

@@ -302,6 +302,11 @@ $.minmax = (value, min, max) ->
 $.hasAudio = (video) ->
   video.mozHasAudio or !!video.webkitAudioDecodedByteCount
 
+$.engine = do ->
+  return 'blink'  if /Chrome\//.test navigator.userAgent
+  return 'webkit' if /WebKit\//.test navigator.userAgent
+  return 'gecko'  if /Gecko\/|Goanna/.test navigator.userAgent # Goanna = Pale Moon 26+
+
 $.item = (key, val) ->
   item = {}
   item[key] = val