Placeholders for markdown editor js and reference to pull it in from

CapaDescriptor. Overrode XMLEditorDescription

common/lib/xmodule/xmodule/capa_module.py

@@ -651,6 +651,8 @@ class CapaDescriptor(RawDescriptor):
     has_score = True
     template_dir_name = 'problem'
     mako_template = "widgets/problem-edit.html"
+    js = {'coffee': [resource_string(__name__, 'js/src/problem/markdown.coffee')]}
+    js_module_name = "MarkdownEditingDescriptor"
 
     # Capa modules have some additional metadata:
     # TODO (vshnayder): do problems have any other metadata?  Do they

common/lib/xmodule/xmodule/js/src/problem/markdown.coffee

@@ -0,0 +1,10 @@
+class @MarkdownEditingDescriptor extends XModule.Descriptor
+  constructor: (@element) ->
+    @edit_box = CodeMirror.fromTextArea($(".edit-box", @element)[0], {
+      mode: "xml"
+      lineNumbers: true
+      lineWrapping: true
+    })
+
+  save: ->
+    data: @edit_box.getValue()