[Switch Access] Reorder functions in MenuManager

Groups static/instance methods and alphabetizes within the groups.

This change reorders functions and makes some functions private, but
has no behavioral change.

Bug: 982004
Change-Id: If2730e9728eaf7459e1e53937adadf3b02d5e0fd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2078214
Commit-Queue: Anastasia Helfinstein <anastasi@google.com>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#745773}

chrome/browser/resources/chromeos/accessibility/switch_access/menu_panel.js

@@ -8,12 +8,6 @@
  */
 class Panel {
   constructor() {
-    /**
-     * The menu manager.
-     * @private {MenuManager}
-     */
-    this.menuManager_;
-
     /**
      * Reference to the menu panel element.
      * @private {Element}
@@ -64,7 +58,7 @@ class Panel {
 
   /** Sets the menu manager to the given object. */
   set menuManager(menuManager) {
-    this.menuManager_ = menuManager;
+    MenuManager.instance = menuManager;
   }
 
   /**
@@ -76,7 +70,7 @@ class Panel {
   setupButton_(button) {
     const action = button.id;
     button.addEventListener('click', function(action) {
-      this.menuManager_.performAction(action);
+      MenuManager.instance.performAction(action);
     }.bind(this, action));
   }
 
@@ -161,7 +155,7 @@ class Panel {
    * @private
    */
   updatePositionAttributes_(buttonOrder, menuId) {
-    this.menuManager_.exit();
+    MenuManager.exit();
     for (let pos = 0; pos < buttonOrder.length; pos++) {
       const buttonPosition = pos;
       const button = document.getElementById(buttonOrder[pos]);