Merge pull request #3732 from minrk/slow-save-on-close

add delay to autosave in beforeunload

allows forceful 'discard changes' by reloading the page and dismissing the warning.
The timer doesn't start until after the dialog is dismissed, so if you decide to nav away without saving changes, the changes will actually not be saved.

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

@@ -368,7 +368,15 @@ var IPython = (function (IPython) {
             // still warn, because if we don't the autosave may fail.
             if (that.dirty && ! that.read_only) {
                 if ( that.autosave_interval ) {
-                    that.save_notebook();
+                    // schedule autosave in a timeout
+                    // this gives you a chance to forcefully discard changes
+                    // by reloading the page if you *really* want to.
+                    // the timer doesn't start until you *dismiss* the dialog.
+                    setTimeout(function () {
+                        if (that.dirty) {
+                            that.save_notebook();
+                        }
+                    }, 1000);
                     return "Autosave in progress, latest changes may be lost.";
                 } else {
                     return "Unsaved changes will be lost.";