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

ui/views/controls/menu/menu_runner_impl.cc

Index: ui/views/controls/menu/menu_runner_impl.cc
diff --git a/ui/views/controls/menu/menu_runner_impl.cc b/ui/views/controls/menu/menu_runner_impl.cc
index 49c34b6ab7a06e8bffc5fe4f7e6853bd4fba564e..96c52923489703fd572ff8b70e8b6d3a2ed76400 100644
--- a/ui/views/controls/menu/menu_runner_impl.cc
+++ b/ui/views/controls/menu/menu_runner_impl.cc
@@ -122,6 +122,9 @@ void MenuRunnerImpl::RunMenuAt(Widget* parent,
     owns_controller_ = true;
   }
   controller->set_is_combobox((run_types & MenuRunner::COMBOBOX) != 0);
+  if (run_types & MenuRunner::FIXED_ANCHOR) {

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

We probably should make ShelfView to call set_cancel_active_touches instead of
relying on |run_types|.

+    controller->set_cancel_active_touches(false);
+  }
   controller_ = controller->AsWeakPtr();
   menu_->set_controller(controller_.get());
   menu_->PrepareForRun(owns_controller_,