Better way of saving through CodeMirror

This should support whatever keyboard shortcuts are configured for the
'save' command.

IPython/html/static/texteditor/js/editor.js

@@ -1,72 +1,74
 // Copyright (c) IPython Development Team.
 // Distributed under the terms of the Modified BSD License.
 
 define([
     'jquery',
     'base/js/utils',
     'codemirror/lib/codemirror',
     'codemirror/mode/meta',
     'codemirror/addon/search/search'
     ],
 function($,
     utils,
     CodeMirror
 ) {
     var Editor = function(selector, options) {
         this.selector = selector;
         this.contents = options.contents;
         this.events = options.events;
         this.base_url = options.base_url;
         this.file_path = options.file_path;
         
         this.codemirror = CodeMirror($(this.selector)[0]);
         
+        // It appears we have to set commands on the CodeMirror class, not the
+        // instance. I'd like to be wrong, but since there should only be one CM
+        // instance on the page, this is good enough for now.
+        CodeMirror.commands.save = $.proxy(this.save, this);
+        
         this.save_enabled = false;
     };
     
     Editor.prototype.load = function() {
         var that = this;
         var cm = this.codemirror;
         this.contents.get(this.file_path, {type: 'file', format: 'text'})
             .then(function(model) {
                 cm.setValue(model.content);
                 
                 // Find and load the highlighting mode
                 var modeinfo = CodeMirror.findModeByMIME(model.mimetype);
                 if (modeinfo) {
                     utils.requireCodeMirrorMode(modeinfo.mode, function() {
                         cm.setOption('mode', modeinfo.mode);
                     });
                 }
                 that.save_enabled = true;
             },
             function(error) {
                 cm.setValue("Error! " + error.message +
                                 "\nSaving disabled.");
                 that.save_enabled = false;
             }
         );
-        cm.setOption("extraKeys", {
-            "Ctrl-S": $.proxy(this.save, this),
-        });
     };
 
     Editor.prototype.save = function() {
         if (!this.save_enabled) {
             console.log("Not saving, save disabled");
             return;
         }
         var model = {
             path: this.file_path,
             type: 'file',
             format: 'text',
             content: this.codemirror.getValue(),
         };
         var that = this;
         this.contents.save(this.file_path, model).then(function() {
             that.events.trigger("save_succeeded.TextEditor");
         });
     };
 
     return {Editor: Editor};
 });