Identify context menus being opened via the long press gesture

ui/base/ui_base_types.h

Index: ui/base/ui_base_types.h
diff --git a/ui/base/ui_base_types.h b/ui/base/ui_base_types.h
index 4ed9f25cfd53b807ac46a839b175754977b7e9f2..4d29bb30d8c6f84dc424b273d6f025307140ec8b 100644
--- a/ui/base/ui_base_types.h
+++ b/ui/base/ui_base_types.h
@@ -47,7 +47,9 @@ enum MenuSourceType {
   MENU_SOURCE_KEYBOARD        = 2,
   MENU_SOURCE_TOUCH           = 3,
   MENU_SOURCE_TOUCH_EDIT_MENU = 4,
-  MENU_SOURCE_TYPE_LAST = MENU_SOURCE_TOUCH_EDIT_MENU
+  MENU_SOURCE_LONG_PRESS      = 5,
+  MENU_SOURCE_LONG_TAP        = 6,
+  MENU_SOURCE_TYPE_LAST = MENU_SOURCE_LONG_TAP
 };
 
 UI_BASE_EXPORT MenuSourceType GetMenuSourceTypeForEvent(const ui::Event& event);