static/tinymce/plugins/autosave/editor_plugin_src.js
function(e) {
				var msg;

				tinymce.each(tinyMCE.editors, function(ed) {
					// Store a draft for each editor instance
					if (ed.plugins.autosave)
						ed.plugins.autosave.storeDraft();

					// Never ask in fullscreen mode
					if (ed.getParam("fullscreen_is_enabled"))
						return;

					// Setup a return message if the editor is dirty
					if (!msg && ed.isDirty() && ed.getParam("autosave_ask_before_unload"))
						msg = ed.getLang("autosave.unload_msg");
				});

				return msg;
			}
function(e) {
				var msg;

				tinymce.each(tinyMCE.editors, function(ed) {
					// Store a draft for each editor instance
					if (ed.plugins.autosave)
						ed.plugins.autosave.storeDraft();

					// Never ask in fullscreen mode
					if (ed.getParam("fullscreen_is_enabled"))
						return;

					// Setup a return message if the editor is dirty
					if (!msg && ed.isDirty() && ed.getParam("autosave_ask_before_unload"))
						msg = ed.getLang("autosave.unload_msg");
				});

				return msg;
			}
Internal unload handler will be called before the page is unloaded