Revert "Re-apply with fixes: Stop using user agent to detect mobile devices. Use a media query and yepnope to load the appropriate css and customizations."

app/helpers/application_helper.rb

@@ -19,6 +19,10 @@ module ApplicationHelper
     end
   end
 
+  def html_classes
+    "#{mobile_view? ? 'mobile-view' : 'desktop-view'} #{mobile_device? ? 'mobile-device' : 'not-mobile-device'}"
+  end
+
   def escape_unicode(javascript)
     if javascript
       javascript = javascript.dup.force_encoding("utf-8")
@@ -111,8 +115,18 @@ module ApplicationHelper
     "#{Discourse::base_uri}/login"
   end
 
-  def stylesheet_filenames(target=:desktop)
-    [asset_path("#{target}.css"), customization_disabled? ? nil : SiteCustomization.custom_stylesheet_path(session[:preview_style], target)].compact
+  def mobile_view?
+    return false unless SiteSetting.enable_mobile_theme
+    if session[:mobile_view]
+      session[:mobile_view] == '1'
+    else
+      mobile_device?
+    end
+  end
+
+  def mobile_device?
+    # TODO: this is dumb. user agent matching is a doomed approach. a better solution is coming.
+    request.user_agent =~ /Mobile|webOS|Nexus 7/ and !(request.user_agent =~ /iPad/)
   end
 
   def customization_disabled?