fixed firefox box-sizing glitch on custom tabs

cms/static/coffee/descriptor/0-1a7d93af49ac6a00461985d16a088dc4.coffee

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

cms/static/coffee/descriptor/0-4455953e190a120e56a33841e5c04a9b.coffee

+class @SequenceDescriptor extends XModule.Descriptor
+  constructor: (@element) ->
+    @$tabs = $(@element).find("#sequence-list")
+    @$tabs.sortable(
+      update: (event, ui) => @update()
+    )
+
+  save: ->
+    children: $('#sequence-list li a', @element).map((idx, el) -> $(el).data('id')).toArray()

cms/static/coffee/descriptor/0-4e077862eb80c378146ab6db01f4c8ef.coffee

+class @JSONEditingDescriptor
+  constructor: (@element) ->
+    @edit_box = CodeMirror.fromTextArea($(".edit-box", @element)[0], {
+      mode: { name: "javascript", json: true }
+    })
+
+  save: -> JSON.parse @edit_box.getValue()

cms/static/coffee/descriptor/0-57c9b4ba234f1f9a74160cd4d61b0869.coffee

+class @JSONEditingDescriptor extends XModule.Descriptor
+  constructor: (@element) ->
+    @edit_box = CodeMirror.fromTextArea($(".edit-box", @element)[0], {
+      mode: { name: "javascript", json: true }
+    })
+
+  save: ->
+    data: JSON.parse @edit_box.getValue()

cms/static/coffee/descriptor/0-8dca6e20f2d4d3fe0e530a877687cb2a.coffee

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

cms/static/coffee/descriptor/0-e867cd6663c4f1d1bc1c20034c69218c.coffee

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

cms/static/coffee/descriptor/0-fdfb7ccca8edfb703fc7a5f124a67f24.coffee

+class @VerticalDescriptor extends XModule.Descriptor
+  constructor: (@element) ->
+    @$items = $(@element).find(".vert-mod")
+    @$items.sortable(
+      update: (event, ui) => @update()
+    )
+
+  save: ->
+    children: $('.vert-mod li', @element).map((idx, el) -> $(el).data('id')).toArray()

lms/static/sass/course/_tabs.scss

 div.static_tab_wrapper {
-
   padding: 2em 2.5em;
+  @include box-sizing(border-box);
 
   h1 {
     @extend .top-header
@@ -9,5 +9,4 @@ div.static_tab_wrapper {
   section {
     margin: 0px 0px 20px;
   }
-
-}
+}
\ No newline at end of file