Fix focusing on image in Firefox.

src/General/Main.coffee

@@ -2,7 +2,9 @@ Main =
   init: ->
     if location.hostname is 'www.google.com'
       type = if location.pathname is '/recaptcha/api/fallback' then 'noscript' else 'v2'
-      return $.ready -> Captcha[type].initFrame()
+      return $.ready ->
+        doc = d.documentElement
+        Captcha[type].initFrame()
 
     g.threads = new SimpleDict()
     g.posts   = new SimpleDict()

src/Posting/Captcha.v2.coffee

@@ -47,7 +47,11 @@ Captcha.v2 =
         for img in images
           img.tabIndex = 0
         if focus
-          images[0].focus()
+          # XXX Image is not focusable at first in Firefox; to be refactored when I figure out why.
+          $.asap ->
+            images[0].focus()
+            d.activeElement is images[0] or not doc.contains images[0]
+          , ->
       fixImages()
       new MutationObserver(fixImages).observe d.body, {childList: true, subtree: true}