BUGFIX: mobile ui was being cached for anon views

lib/mobile_detection.rb

@@ -0,0 +1,19 @@
+module MobileDetection
+  def self.mobile_device?(user_agent)
+    # TODO: this is dumb. user agent matching is a doomed approach. a better solution is coming.
+    user_agent =~ /Mobile|webOS|Nexus 7/ && !(user_agent =~ /iPad/)
+  end
+
+  # we need this as a reusable chunk that is called from the cache
+  def self.resolve_mobile_view!(user_agent, params, session)
+    return false unless SiteSetting.enable_mobile_theme
+
+    session[:mobile_view] = params[:mobile_view] if params.has_key?(:mobile_view)
+
+    if session[:mobile_view]
+      session[:mobile_view] == '1'
+    else
+      mobile_device?(user_agent)
+    end
+  end
+end