Fix duplicate announcement for apps in grid

Changes:
Use ax::mojom::Event::kFocus instead of ax::mojom::Event::kSelection
since the latter will trigger duplicate vox announcement.

Bug: 929762
Change-Id: I6757daa139cefac303f607de0346a70cb3138d08
Reviewed-on: https://chromium-review.googlesource.com/c/1459056Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630087}

ash/app_list/views/apps_grid_view.cc

@@ -1118,7 +1118,7 @@ void AppsGridView::SetSelectedItemByIndex(const GridIndex& index) {
   EnsureViewVisible(index);
   selected_view_ = new_selection;
   selected_view_->SchedulePaint();
-  selected_view_->NotifyAccessibilityEvent(ax::mojom::Event::kSelection, true);
+  selected_view_->NotifyAccessibilityEvent(ax::mojom::Event::kFocus, true);
 }
 
 GridIndex AppsGridView::GetIndexOfView(const AppListItemView* view) const {

ash/app_list/views/suggestion_chip_view.cc

@@ -148,7 +148,7 @@ void SuggestionChipView::OnPaintBackground(gfx::Canvas* canvas) {
 
 void SuggestionChipView::OnFocus() {
   SchedulePaint();
-  NotifyAccessibilityEvent(ax::mojom::Event::kSelection, true);
+  NotifyAccessibilityEvent(ax::mojom::Event::kFocus, true);
 }
 
 void SuggestionChipView::OnBlur() {