fix body overflow on dashboard

IPython/frontend/html/notebook/static/css/style.min.css

@@ -12,7 +12,8 b''
 .end{-webkit-box-pack:end;-moz-box-pack:end;box-pack:end;}
 .center{-webkit-box-pack:center;-moz-box-pack:center;box-pack:center;}
 .corner-all{border-radius:3px;}
-body{overflow:hidden;background-color:#ffffff;}
+body{background-color:#ffffff;}
+body.notebook_app{overflow:hidden;}
 blockquote{border-left:4px solid #DDD;padding:0 15px;color:#777;}
 span#save_widget{padding:5px;margin:0px 0px 0px 300px;display:inline-block;}
 span#notebook_name{height:1em;line-height:1em;padding:3px;border:none;font-size:146.5%;}

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

@@ -7,9 +7,12 b''
 @import "variables.less";
 
 body {
-    overflow: hidden;
     background-color:@notebook_background;
 }
+    
+body.notebook_app {
+    overflow: hidden;
+}
 
 blockquote {
     border-left: 4px solid #DDD;

IPython/frontend/html/notebook/templates/notebook.html

@@ -33,6 +33,7 b' data-base-project-url={{base_project_url}}'
 data-base-kernel-url={{base_kernel_url}}
 data-read-only={{read_only and not logged_in}}
 data-notebook-id={{notebook_id}}
+class="notebook_app"
 
 {% endblock %}