Fetch the image's HEAD status to see if it's still available or not.

Chrome bypasses the lack of CORS because we've allowed `i.4cdn.org` in the manifest.

src/Images/ImageExpand.coffee

@@ -132,6 +132,15 @@ ImageExpand =
         return
 
     timeoutID = setTimeout ImageExpand.expand, 10000, post
+    <% if (type === 'crx') { %>
+    $.ajax @src,
+      onloadend: ->
+        return if @status isnt 404
+        clearTimeout timeoutID
+        post.kill true
+    ,
+      type: 'head'
+    <% } else { %>
     # XXX CORS for i.4cdn.org WHEN?
     $.ajax "//a.4cdn.org/#{post.board}/res/#{post.thread}.json", onload: ->
       return if @status isnt 200
@@ -143,6 +152,7 @@ ImageExpand =
       else if postObj.filedeleted
         clearTimeout timeoutID
         post.kill true
+    <% } %>
 
   menu:
     init: ->

src/Images/ImageHover.coffee

@@ -38,6 +38,15 @@ ImageHover =
         return
 
     timeoutID = setTimeout (=> @src = post.file.URL + '?' + Date.now()), 3000
+    <% if (type === 'crx') { %>
+    $.ajax @src,
+      onloadend: ->
+        return if @status isnt 404
+        clearTimeout timeoutID
+        post.kill true
+    ,
+      type: 'head'
+    <% } else { %>
     # XXX CORS for i.4cdn.org WHEN?
     $.ajax "//a.4cdn.org/#{post.board}/res/#{post.thread}.json", onload: ->
       return if @status isnt 200
@@ -49,3 +58,4 @@ ImageHover =
       else if postObj.filedeleted
         clearTimeout timeoutID
         post.kill true
+    <% } %>