Remove unused ash::SHELF_ALIGNMENT_TOP

ash/shelf/shelf_tooltip_manager.cc

Index: ash/shelf/shelf_tooltip_manager.cc
diff --git a/ash/shelf/shelf_tooltip_manager.cc b/ash/shelf/shelf_tooltip_manager.cc
index 92621dadeecba91b6dcf2506955993194bd9c9b4..0476fd6e9db3991825f3a80f02b3320220c0600f 100644
--- a/ash/shelf/shelf_tooltip_manager.cc
+++ b/ash/shelf/shelf_tooltip_manager.cc
@@ -147,7 +147,7 @@ void ShelfTooltipManager::ShowTooltip(views::View* view) {
   Shelf* shelf = shelf_view_->shelf();
   views::BubbleBorder::Arrow arrow = shelf->SelectValueForShelfAlignment(
       views::BubbleBorder::BOTTOM_CENTER, views::BubbleBorder::LEFT_CENTER,
-      views::BubbleBorder::RIGHT_CENTER, views::BubbleBorder::TOP_CENTER);
+      views::BubbleBorder::RIGHT_CENTER);
 
   base::string16 text = shelf_view_->GetTitleForView(view);
   bubble_ = new ShelfTooltipBubble(view, arrow, text);