Make shelf item can be dragged when context menu is opened.

ui/views/controls/menu/menu_host.h

Index: ui/views/controls/menu/menu_host.h
diff --git a/ui/views/controls/menu/menu_host.h b/ui/views/controls/menu/menu_host.h
index 484b90889320a3c7c05724aacfbab234382db741..70ae2e74c598b8fc02d43cfd2f39aa3d9b637b73 100644
--- a/ui/views/controls/menu/menu_host.h
+++ b/ui/views/controls/menu/menu_host.h
@@ -78,6 +78,11 @@ class MenuHost : public Widget {
   void OnDragWillStart() override;
   void OnDragComplete() override;
 
+#if !defined(OS_MACOSX)

[msw, 2017/05/17 23:03:30]

ditto question. If you keep all these blocks, commend on the #else and #endif to
point out what block it's part of (ie. #endif  // !defined(OS_MACOSX))

[minch1, 2017/05/26 23:01:14]

Done.

+  // Parent of the MenuHost widget.
+  Widget* owner_ = nullptr;
+#endif
+
   // The view we contain.
   SubmenuView* submenu_;