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

ui/views/controls/menu/submenu_view.cc

Index: ui/views/controls/menu/submenu_view.cc
diff --git a/ui/views/controls/menu/submenu_view.cc b/ui/views/controls/menu/submenu_view.cc
index 5f3b54c787cc7cb8ffa33910199d584172e4aa5e..22012841030bb163ec382bcca70fca03f9d18e41 100644
--- a/ui/views/controls/menu/submenu_view.cc
+++ b/ui/views/controls/menu/submenu_view.cc
@@ -367,9 +367,10 @@ bool SubmenuView::IsShowing() {
 
 void SubmenuView::ShowAt(Widget* parent,
                          const gfx::Rect& bounds,
-                         bool do_capture) {
+                         bool do_capture,
+                         bool cancel_active_touches) {

[xiyuan, 2017/05/12 20:24:57]

ditto, get |cancel_active_touches| from MenuController ?

   if (host_) {
-    host_->ShowMenuHost(do_capture);
+    host_->ShowMenuHost(do_capture, cancel_active_touches);
   } else {
     host_ = new MenuHost(this);
     // Force construction of the scroll view container.
@@ -377,7 +378,8 @@ void SubmenuView::ShowAt(Widget* parent,
     // Force a layout since our preferred size may not have changed but our
     // content may have.
     InvalidateLayout();
-    host_->InitMenuHost(parent, bounds, scroll_view_container_, do_capture);
+    host_->InitMenuHost(parent, bounds, scroll_view_container_, do_capture,
+                        cancel_active_touches);
   }
 
   GetScrollViewContainer()->NotifyAccessibilityEvent(