Use link+blob urls for the stylesheet. That'll help me inspect the css.

I wonder if it matters performance-wise.

4chan_x.user.js

@@ -733,10 +733,17 @@
         return setTimeout($.asap, 25, test, cb);
       }
     },
-    addStyle: function(css) {
+    addStyle: function(css, type) {
       var style;
-      style = $.el('style', {
+      style = type === 'style' || !window.URL ? $.el('style', {
         textContent: css
+      }) : $.el('link', {
+        rel: 'stylesheet',
+        href: URL.createObjectURL(new Blob([css]))
+      }, {
+        type: 'text/css'
+      }, {
+        title: g.NAMESPACE
       });
       $.asap((function() {
         return d.head;
@@ -3505,7 +3512,7 @@
         if (checked) {
           $.on(window, 'resize', ImageExpand.resize);
           if (!ImageExpand.style) {
-            ImageExpand.style = $.addStyle('');
+            ImageExpand.style = $.addStyle(null, 'style');
           }
           return ImageExpand.resize();
         } else {
@@ -4474,7 +4481,7 @@
       }
 
       _Class.prototype.setFile = function(file) {
-        var fileUrl, img, url,
+        var fileUrl, img,
           _this = this;
         this.file = file;
         this.el.title = "" + file.name + " (" + ($.bytesToString(file.size)) + ")";
@@ -4485,10 +4492,10 @@
           this.el.style.backgroundImage = null;
           return;
         }
-        if (!(url = window.URL || window.webkitURL)) {
+        if (!window.URL) {
           return;
         }
-        url.revokeObjectURL(this.url);
+        URL.revokeObjectURL(this.url);
         fileUrl = url.createObjectURL(file);
         img = $.el('img');
         $.on(img, 'load', function() {
@@ -4516,17 +4523,16 @@
           for (i = _i = 0; 0 <= l ? _i < l : _i > l; i = 0 <= l ? ++_i : --_i) {
             ui8a[i] = data.charCodeAt(i);
           }
-          _this.url = url.createObjectURL(new Blob([ui8a], {
+          _this.url = URL.createObjectURL(new Blob([ui8a], {
             type: 'image/png'
           }));
           _this.el.style.backgroundImage = "url(" + _this.url + ")";
-          return typeof url.revokeObjectURL === "function" ? url.revokeObjectURL(fileUrl) : void 0;
+          return URL.revokeObjectURL(fileUrl);
         });
         return img.src = fileUrl;
       };
 
       _Class.prototype.rmFile = function() {
-        var _base;
         QR.resetFileInput();
         delete this.file;
         this.el.title = null;
@@ -4534,7 +4540,10 @@
         if (QR.spoiler) {
           $('label', this.el).hidden = true;
         }
-        return typeof (_base = window.URL || window.webkitURL).revokeObjectURL === "function" ? _base.revokeObjectURL(this.url) : void 0;
+        if (!window.URL) {
+          return;
+        }
+        return URL.revokeObjectURL(this.url);
       };
 
       _Class.prototype.select = function() {
@@ -4599,7 +4608,7 @@
       };
 
       _Class.prototype.rm = function() {
-        var index, _ref;
+        var index;
         QR.resetFileInput();
         $.rm(this.el);
         index = QR.replies.indexOf(this);
@@ -4609,7 +4618,10 @@
           (QR.replies[index - 1] || QR.replies[index + 1]).select();
         }
         QR.replies.splice(index, 1);
-        return (_ref = window.URL || window.webkitURL) != null ? _ref.revokeObjectURL(this.url) : void 0;
+        if (!window.URL) {
+          return;
+        }
+        return URL.revokeObjectURL(this.url);
       };
 
       return _Class;

lib/$.coffee

@@ -83,9 +83,16 @@ $.extend $,
       cb()
     else
       setTimeout $.asap, 25, test, cb
-  addStyle: (css) ->
-    style = $.el 'style',
-      textContent: css
+  addStyle: (css, type) ->
+    style = if type is 'style' or !window.URL
+      $.el 'style',
+        textContent: css
+    else
+      $.el 'link',
+        rel: 'stylesheet'
+        href: URL.createObjectURL new Blob [css],
+          type: 'text/css'
+        title: g.NAMESPACE
     $.asap (-> d.head), ->
       $.add d.head, style
     style

src/features.coffee

@@ -2134,7 +2134,7 @@ ImageExpand =
       if checked
         $.on window, 'resize', ImageExpand.resize
         unless ImageExpand.style
-          ImageExpand.style = $.addStyle ''
+          ImageExpand.style = $.addStyle null, 'style'
         ImageExpand.resize()
       else
         $.off window, 'resize', ImageExpand.resize

src/qr.coffee

@@ -351,9 +351,9 @@ QR =
       unless /^image/.test file.type
         @el.style.backgroundImage = null
         return
-      # XXX Opera does not support window.URL
-      return unless url = window.URL or window.webkitURL
-      url.revokeObjectURL @url
+      # XXX Opera does not support blob URL
+      return unless window.URL
+      URL.revokeObjectURL @url
 
       # Create a redimensioned thumbnail.
       fileUrl = url.createObjectURL file
@@ -388,9 +388,9 @@ QR =
         for i in  [0...l]
           ui8a[i] = data.charCodeAt i
 
-        @url = url.createObjectURL new Blob [ui8a], type: 'image/png'
+        @url = URL.createObjectURL new Blob [ui8a], type: 'image/png'
         @el.style.backgroundImage = "url(#{@url})"
-        url.revokeObjectURL? fileUrl
+        URL.revokeObjectURL fileUrl
 
       img.src = fileUrl
     rmFile: ->
@@ -399,7 +399,8 @@ QR =
       @el.title = null
       @el.style.backgroundImage = null
       $('label', @el).hidden = true if QR.spoiler
-      (window.URL or window.webkitURL).revokeObjectURL? @url
+      return unless window.URL
+      URL.revokeObjectURL @url
     select: ->
       QR.selected?.el.id = null
       QR.selected = @
@@ -446,7 +447,8 @@ QR =
       else if @el.id is 'selected'
         (QR.replies[index-1] or QR.replies[index+1]).select()
       QR.replies.splice index, 1
-      (window.URL or window.webkitURL)?.revokeObjectURL @url
+      return unless window.URL
+      URL.revokeObjectURL @url
 
   captcha:
     init: ->