Allow menus to stay open during a child view's drag and drop

ui/views/controls/menu/menu_host.cc

Index: ui/views/controls/menu/menu_host.cc
diff --git a/ui/views/controls/menu/menu_host.cc b/ui/views/controls/menu/menu_host.cc
index 2716ec8bb782c1a46288c0ab449d80a2a96e2caf..90192405a667c0d7ab15544ca57d70b584120aea 100644
--- a/ui/views/controls/menu/menu_host.cc
+++ b/ui/views/controls/menu/menu_host.cc
@@ -110,8 +110,11 @@ void MenuHost::OnMouseCaptureLost() {
     return;
   MenuController* menu_controller =
       submenu_->GetMenuItem()->GetMenuController();
-  if (menu_controller && !menu_controller->drag_in_progress())
+  if (menu_controller &&
+      !menu_controller->drag_in_progress() &&
+      !dragged_view()) {

[sky, 2014/07/11 17:45:33]

Document why we check dragged_view(). I also midly prefer putting as much on one
line as possible, in other words merge 113 and 114.

[Devlin, 2014/07/11 18:43:51]

If we forward a OnDragWillStart() down to MenuController, I don't think we need
to check dragged view anymore, because drag_in_progress will actually be true
here.  Right?

[sky, 2014/07/11 19:15:20]

Yes, I believe you are right.

     menu_controller->CancelAll();
+  }
   Widget::OnMouseCaptureLost();
 }
 
@@ -135,4 +138,10 @@ void MenuHost::OnOwnerClosing() {
     menu_controller->CancelAll();
 }
 
+void MenuHost::OnDragComplete() {
+  // During a view's drag, we may have lost the capture. Reset it so that we

[sky, 2014/07/11 17:45:33]

Add a delegate method as to what should happen when the drag is completed. The
default implementation should return a value indicating the menu should close.
WrenchMenu would return otherwise. This code should just call through to the
MenuController and let it do the right thing.

[Devlin, 2014/07/11 18:43:51]

Done.  However, this has a side-effect: other drags in the wrench menu (e.g.,
bookmarks) now behave differently than they used to.  Is this okay?

[sky, 2014/07/11 19:15:20]

Good point. I don't believe the bookmark code does the right thing in the cast,
so you should cancel on a drag from bookmarks. The delegate should only be
consulted on drags initiated outside of menu code.

[Devlin, 2014/07/11 20:28:15]

Tentatively done (see comment on new patch set).

+  // get OnMouseCaptureLost events.
+  native_widget_private()->SetCapture();
+}
+
 }  // namespace views