Fix editing of html modules that broke with changes to EditingDescriptor

common/lib/xmodule/xmodule/editing_module.py

 from pkg_resources import resource_string
-from lxml import etree
 from xmodule.mako_module import MakoModuleDescriptor
 import logging
 

common/lib/xmodule/xmodule/html_module.py

@@ -6,7 +6,8 @@ import sys
 from lxml import etree
 from path import path
 
-from .x_module import XModule, Template
+from .x_module import XModule
+from pkg_resources import resource_string
 from .xml_module import XmlDescriptor, name_to_pathname
 from .editing_module import EditingDescriptor
 from .stringify import stringify_children
@@ -34,6 +35,9 @@ class HtmlDescriptor(XmlDescriptor, EditingDescriptor):
     module_class = HtmlModule
     filename_extension = "xml"
 
+    js = {'coffee': [resource_string(__name__, 'js/src/html/edit.coffee')]}
+    js_module_name = "HTMLEditingDescriptor"
+
     # VS[compat] TODO (cpennington): Delete this method once all fall 2012 course
     # are being edited in the cms
     @classmethod

common/lib/xmodule/xmodule/js/src/html/edit.coffee

+class @HTMLEditingDescriptor
+  constructor: (@element) ->
+    @edit_box = CodeMirror.fromTextArea($(".edit-box", @element)[0], {
+      mode: "text/html"
+    })
+
+  save: -> @edit_box.getValue()