Do not scroll when closing the menu with space

Fixes #1082

Author: notriddle

static/menu.js

@@ -128,15 +128,22 @@
                     break;
                 case "enter":
                 case "return":
-                case "space":
-                case " ":
-                    // enter, return, and space have the default browser behavior,
+                    // enter and return have the default browser behavior,
                     // but they also close the menu
                     // this behavior is identical between both the WAI example, and GitHub's
                     setTimeout(function() {
                         closeMenu();
                     }, 100);
                     break;
+                case "space":
+                case " ":
+                    // space closes the menu, but does not engage default behavior,
+                    // which would be to scroll the page
+                    // this behavior is identical between both the WAI example, and GitHub's
+                    closeMenu();
+                    e.preventDefault();
+                    e.stopPropagation();
+                    break;
                 case "home":
                 case "pageup":
                     // home: focus first menu item.