Improve zen mode internals.

app/assets/javascripts/zen_mode.js.coffee

 class @ZenMode
   @fullscreen_prefix = 'fullscreen_'
-  @ESC = 27
 
   constructor: ->
     @active_zen_area = null
     @active_checkbox = null
 
     $('body').on 'change', '.zennable input[type=checkbox]', (e) =>
-      checkbox = e.currentTarget;
+      checkbox = e.currentTarget
       if checkbox.checked
         Mousetrap.pause()
         @udpateActiveZenArea(checkbox)
@@ -15,8 +14,7 @@ class @ZenMode
         @exitZenMode()
 
     $(document).on 'keydown', (e) =>
-      console.log("esc")
-      if e.keyCode is ZenMode.ESC
+      if e.keyCode is $.ui.keyCode.ESCAPE
         @exitZenMode()
 
     $(window).on 'hashchange', @updateZenModeFromLocationHash