Fix broken "Raw cell MIME type" dialog (#3255) (#5385)

The modal dialog for entering a custom MIME type for a "Raw NBConvert"-
type cell was broken. This change to the JavaScript code makes the modal
dialog appear correctly again, as well as correctly disabling the
handling of key presses by the cell editor while the dialog is open.

This fixes #3255.

Author: Onno Broekmans

notebook/static/notebook/js/celltoolbarpresets/rawcell.js

@@ -26,22 +26,35 @@ define([
       function(cell, value) {
         if (value === "-") {
           delete cell.metadata.raw_mimetype;
-        } else if (value === 'dialog'){
-            var dialog = $('<div/>').append(
-                $("<p/>")
-                    .text(i18n.msg._("Set the MIME type of the raw cell:"))
-            ).append(
-                $("<br/>")
-            ).append(
-                $('<input/>').attr('type','text').attr('size','25')
-                .val(cell.metadata.raw_mimetype || "-")
-            );
+        } else if (value === 'dialog') {
+            var message =
+                i18n.msg._("Set the MIME type of the raw cell:");
+
+            var mimeinput = $('<input/>')
+                .attr('type', 'text')
+                .attr('size', '25')
+                .attr('name', 'mimetype')
+                .val(cell.metadata.raw_mimetype || "-");
+
+            var dialogform = $('<div/>').attr('title', i18n.msg._("Edit MIME type"))
+                .append(
+                    $('<form/>').append(
+                        $('<fieldset/>').append(
+                            $('<label/>')
+                            .attr('for', 'mimetype')
+                            .text(message)
+                            )
+                        .append($('<br/>'))
+                        .append(mimeinput)
+                        )
+                );
+
             dialog.modal({
                 title: i18n.msg._("Raw Cell MIME Type"),
-                body: dialog,
+                body: dialogform,
                 buttons : {
-                    "Cancel": {},
-                    "OK": {
+                    Cancel: {},
+                    OK: {
                         class: "btn-primary",
                         click: function () {
                             console.log(cell);
@@ -50,6 +63,8 @@ define([
                         }
                     }
                 },
+                notebook: cell.notebook,
+                keyboard_manager: cell.keyboard_manager,
                 open : function (event, ui) {
                     var that = $(this);
                     // Upon ENTER, click the OK button.