TileItemView: Fixed ChromeVox selection upon deselection.

BUG=459872

Review URL: https://codereview.chromium.org/935143005

Cr-Commit-Position: refs/heads/master@{#317018}

ui/app_list/views/tile_item_view.cc

@@ -56,7 +56,9 @@ void TileItemView::SetSelected(bool selected) {
 
   selected_ = selected;
   UpdateBackgroundColor();
-  NotifyAccessibilityEvent(ui::AX_EVENT_FOCUS, true);
+
+  if (selected)
+    NotifyAccessibilityEvent(ui::AX_EVENT_FOCUS, true);
 }
 
 void TileItemView::SetParentBackgroundColor(SkColor color) {