movestyling from js to css

IPython/html/static/notebook/js/main.js

@@ -42,8 +42,6 b' require(['
     ) {
     "use strict";
 
-    $('div#notebook_panel').addClass('border-box-sizing');
-
     var common_options = {
         base_url : utils.get_body_data("baseUrl"),
         ws_url : IPython.utils.get_body_data("wsUrl"),

IPython/html/static/notebook/less/notebook.less

@@ -31,6 +31,7 b' div#notebook_panel {'
     margin: 0px 0px 0px 0px;
     padding: 0px;
     .box-shadow(@notebook-shadow);
+    .border-box-sizing();
 }
 div#notebook {
     font-size: @notebook_font_size;