Move shelf item tooltip flag from delegate to item.

ash/common/shelf/app_list_shelf_item_delegate.cc

Index: ash/common/shelf/app_list_shelf_item_delegate.cc
diff --git a/ash/common/shelf/app_list_shelf_item_delegate.cc b/ash/common/shelf/app_list_shelf_item_delegate.cc
index 93b8a10e63ff734b20437f651a85634140fc6569..7f7c3db787ef712c61a95c6f3424bf3ab4ae7f01 100644
--- a/ash/common/shelf/app_list_shelf_item_delegate.cc
+++ b/ash/common/shelf/app_list_shelf_item_delegate.cc
@@ -63,10 +63,6 @@ bool AppListShelfItemDelegate::CanPin() const {
   return true;
 }
 
-bool AppListShelfItemDelegate::ShouldShowTooltip() {
-  return true;
-}
-
 void AppListShelfItemDelegate::Close() {}
 
 }  // namespace ash