Move enum MenuAnchorPosition to reduce deps on menu_item_view.h

ui/message_center/views/message_view_context_menu_controller.cc

Index: ui/message_center/views/message_view_context_menu_controller.cc
diff --git a/ui/message_center/views/message_view_context_menu_controller.cc b/ui/message_center/views/message_view_context_menu_controller.cc
index 6dcae7c22a5f971e9dc35ee459e3aaf2251b7cc8..93601e5cfff60c22948d7e0b3cb126360d533679 100644
--- a/ui/message_center/views/message_view_context_menu_controller.cc
+++ b/ui/message_center/views/message_view_context_menu_controller.cc
@@ -34,13 +34,12 @@ void MessageViewContextMenuController::ShowContextMenuForView(
 
   views::MenuRunner menu_runner(menu_model.get());
 
-  ignore_result(menu_runner.RunMenuAt(
-      source->GetWidget()->GetTopLevelWidget(),
-      NULL,
-      gfx::Rect(point, gfx::Size()),
-      views::MenuItemView::TOPRIGHT,
-      source_type,
-      views::MenuRunner::HAS_MNEMONICS));
+  ignore_result(menu_runner.RunMenuAt(source->GetWidget()->GetTopLevelWidget(),
+                                      NULL,
+                                      gfx::Rect(point, gfx::Size()),
+                                      ui::MENU_ANCHOR_TOPRIGHT,
+                                      source_type,
+                                      views::MenuRunner::HAS_MNEMONICS));
 }
 
 }  // namespace message_center