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

ui/views/controls/menu/menu_controller.cc

Index: ui/views/controls/menu/menu_controller.cc
diff --git a/ui/views/controls/menu/menu_controller.cc b/ui/views/controls/menu/menu_controller.cc
index a5ecb7df05c4a3fc1bda4e00ee870b38a24475e9..a57f16f89c50d30aea40769780ad0c8d82123f95 100644
--- a/ui/views/controls/menu/menu_controller.cc
+++ b/ui/views/controls/menu/menu_controller.cc
@@ -820,8 +820,12 @@ void MenuController::OnGestureEvent(SubmenuView* source,
   if (event->stopped_propagation())
       return;
 
-  if (!part.submenu)
+  if (!part.submenu) {
+    event->ConvertLocationToTarget(source->GetWidget()->GetNativeWindow(),
+                                   owner()->GetNativeWindow());
+    owner()->OnGestureEvent(event);
     return;
+  }

[xiyuan, 2017/05/12 20:24:56]

nit: revist to something like

if (part.submenu) {
  part.submenu->OnGestureEvent(event);
  return;
}

// Forwarding to owner if necessary. We might want to use
// |cancel_active_touches_| as a flag as whether to do the
// forwarding.

   part.submenu->OnGestureEvent(event);
 }
 
@@ -1824,7 +1828,8 @@ void MenuController::OpenMenuImpl(MenuItemView* item, bool show) {
     // Menus are the only place using kGroupingPropertyKey, so any value (other
     // than 0) is fine.
     const int kGroupingId = 1001;
-    item->GetSubmenu()->ShowAt(owner_, bounds, do_capture);
+    item->GetSubmenu()->ShowAt(owner_, bounds, do_capture,
+                               cancel_active_touches_);
     item->GetSubmenu()->GetWidget()->SetNativeWindowProperty(
         TooltipManager::kGroupingPropertyKey,
         reinterpret_cast<void*>(kGroupingId));