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

ui/views/controls/menu/menu_runner.h

Index: ui/views/controls/menu/menu_runner.h
diff --git a/ui/views/controls/menu/menu_runner.h b/ui/views/controls/menu/menu_runner.h
index abba98e9dd4095862b385ff57b26a6b49f3e2789..4ab25e2054396a7e94ffc3ea524330768694e01d 100644
--- a/ui/views/controls/menu/menu_runner.h
+++ b/ui/views/controls/menu/menu_runner.h
@@ -89,6 +89,11 @@ class VIEWS_EXPORT MenuRunner {
     // Menu with fixed anchor position, so |MenuRunner| will not attempt to
     // adjust the anchor point. For example the context menu of shelf item.
     FIXED_ANCHOR = 1 << 6,
+
+    // Owner of the menu can be dragged after menu is created and dragging will
+    // close the menu. For example the shelf item can be dragged when the
+    // context menu of the item is opened.

[xiyuan, 2017/05/26 23:13:38]

nit: I would say something like

// Owner of the menu could be in the middle of a gesture when the menu
// opens and can use this flag to continue the gesture. For example,
// shelf uses the flag to continue dragging an item without lifting the
// finger after the context menu of the item is opened.

[minch1, 2017/06/01 16:42:28]

Done.

+    PRESERVE_CURRENT_GESTURE_FOR_OWNER = 1 << 7,
   };
 
   // Creates a new MenuRunner, which may use a native menu if available.