FIX: favicon update broken when favicon lived on a CDN

app/assets/javascripts/discourse.js

@@ -57,7 +57,11 @@ window.Discourse = Ember.Application.createWithMixins(Discourse.Ajax, {
 
   faviconChanged: function() {
     if(Discourse.User.currentProp('dynamic_favicon')) {
-      new Favcount(Discourse.SiteSettings.favicon_url).set(
+      var url = Discourse.SiteSettings.favicon_url;
+      if (/^http/.test(url)) {
+        url = Discourse.getURL("/favicon/proxied?" + encodeURIComponent(url));
+      }
+      new Favcount(url).set(
         this.get('notifyCount')
       );
     }

app/controllers/static_controller.rb

@@ -1,7 +1,10 @@
+require_dependency 'distributed_memoizer'
+require_dependency 'file_helper'
+
 class StaticController < ApplicationController
 
   skip_before_filter :check_xhr, :redirect_to_login_if_required
-  skip_before_filter :verify_authenticity_token, only: [:enter]
+  skip_before_filter :verify_authenticity_token, only: [:cdn_asset, :enter, :favicon]
 
   def show
     return redirect_to(path '/') if current_user && params[:id] == 'login'
@@ -82,7 +85,28 @@ class StaticController < ApplicationController
     redirect_to destination
   end
 
-  skip_before_filter :verify_authenticity_token, only: [:cdn_asset]
+  # We need to be able to draw our favicon on a canvas
+  # and pull it off the canvas into a data uri
+  # This can work by ensuring people set all the right CORS
+  # settings in the CDN asset, BUT its annoying and error prone
+  # instead we cache the favicon in redis and serve it out real quick with
+  # a huge expiry, we also cache these assets in nginx so it bypassed if needed
+  def favicon
+
+    data = DistributedMemoizer.memoize('favicon' + SiteSetting.favicon_url, 60*60*24) do
+      file = FileHelper.download(SiteSetting.favicon_url, 50.kilobytes, "favicon.png")
+      data = file.read
+      file.unlink
+      data
+    end
+
+    expires_in 1.year, public: true
+    response.headers["Expires"] = 1.year.from_now.httpdate
+    response.headers["Content-Length"] = data.bytesize.to_s
+    response.headers["Last-Modified"] = Time.new('2000-01-01').httpdate
+    render text: data, content_type: "image/png"
+  end
+
 
   def cdn_asset
     path = File.expand_path(Rails.root + "public/assets/" + params[:path])