Add ContextMenuSourceType to views::ContextMenuController::ShowContextMenuForView.

ui/views/controls/combobox/native_combobox_views.cc

Index: ui/views/controls/combobox/native_combobox_views.cc
diff --git a/ui/views/controls/combobox/native_combobox_views.cc b/ui/views/controls/combobox/native_combobox_views.cc
index 791598b7cbcdd22b5f40ead486c2b6861d6b3f0c..684f87db2f6627452d9ca870e3ff30c9e108dba5 100644
--- a/ui/views/controls/combobox/native_combobox_views.cc
+++ b/ui/views/controls/combobox/native_combobox_views.cc
@@ -397,7 +397,8 @@ void NativeComboboxViews::ShowDropDownMenu() {
   dropdown_open_ = true;
   if (dropdown_list_menu_runner_->RunMenuAt(
           GetWidget(), NULL, bounds, MenuItemView::TOPLEFT,
-          MenuRunner::HAS_MNEMONICS) == MenuRunner::MENU_DELETED)
+          ui::MENU_SOURCE_NONE, MenuRunner::HAS_MNEMONICS) ==
+      MenuRunner::MENU_DELETED)
     return;
   dropdown_open_ = false;