Fire exactly one selection event when hovering over new menu item

Adjust menu controller to ensure correct number of kSelection events.
These are turned into focus events under MSAA.

- Regular menu items: we were firing extra events even when selection
  didn't change.
- Hot button menu items, such as zoom-related, cut/copy/paste in edit
  menu, were not firing any events on hover, because the button already
  considered itself hot tracked via the button controller's mouse
  handling.

AX-Relnotes: avoid missing or duplicate menu item announcements when using mouse
Bug: 1077755, 1106916
Change-Id: Ie933146b647d56f7665cfc72bb708e9f7bdd71de
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2350483
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797288}

ui/views/controls/menu/menu_controller.cc

@@ -1381,7 +1381,7 @@ void MenuController::SetSelection(MenuItemView* menu_item,
     StartShowTimer();
 
   // Notify an accessibility focus event on all menu items except for the root.
-  if (menu_item &&
+  if (menu_item && pending_item_changed &&
       (MenuDepth(menu_item) != 1 ||
        menu_item->GetType() != MenuItemView::Type::kSubMenu ||
        (menu_item->GetType() == MenuItemView::Type::kActionableSubMenu &&
@@ -3117,16 +3117,19 @@ void MenuController::SetNextHotTrackedView(
   SetInitialHotTrackedView(to_select, direction);
 }
 
-void MenuController::SetHotTrackedButton(Button* hot_button) {
+void MenuController::SetHotTrackedButton(Button* new_hot_button) {
+  if (hot_button_ == new_hot_button)
+    return;
+
   // If we're providing a new hot-tracked button, first remove the existing one.
-  if (hot_button_ && hot_button_ != hot_button) {
+  if (hot_button_) {
     hot_button_->SetHotTracked(false);
     hot_button_->GetViewAccessibility().EndPopupFocusOverride();
   }
 
   // Then set the new one.
-  hot_button_ = hot_button;
-  if (hot_button_ && !hot_button_->IsHotTracked()) {
+  hot_button_ = new_hot_button;
+  if (hot_button_) {
     hot_button_->GetViewAccessibility().SetPopupFocusOverride();
     hot_button_->SetHotTracked(true);
     hot_button_->NotifyAccessibilityEvent(ax::mojom::Event::kSelection, true);

ui/views/controls/menu/menu_controller.h

@@ -612,7 +612,7 @@ class VIEWS_EXPORT MenuController
                              SelectionIncrementDirectionType direction);
 
   // Updates the current |hot_button_| and its hot tracked state.
-  void SetHotTrackedButton(Button* hot_button);
+  void SetHotTrackedButton(Button* new_hot_button);
 
   // Returns whether typing a new character will continue the existing prefix
   // selection. If this returns false, typing a new character will start a new