Make WindowTree::SetModal() take the type.

ui/aura/mus/window_tree_client.cc

Index: ui/aura/mus/window_tree_client.cc
diff --git a/ui/aura/mus/window_tree_client.cc b/ui/aura/mus/window_tree_client.cc
index 0f7351c738917443789d004d657cba9e57e89b8b..934e74dff85caa4f4539f084b9acaced362d1727 100644
--- a/ui/aura/mus/window_tree_client.cc
+++ b/ui/aura/mus/window_tree_client.cc
@@ -479,18 +479,10 @@ bool WindowTreeClient::HandleInternalPropertyChanged(WindowMus* window,
   if (key != client::kModalKey)
     return false;
 
-  if (window->GetWindow()->GetProperty(client::kModalKey) ==
-      ui::MODAL_TYPE_NONE) {
-    // TODO: shouldn't early return, but explicitly tell server to turn off
-    // modality. http://crbug.com/660073.
-    return true;
-  }
-
   const uint32_t change_id =
       ScheduleInFlightChange(base::MakeUnique<InFlightSetModalChange>(window));
-  // TODO: this is subtly different that explicitly specifying a type.
-  // http://crbug.com/660073.
-  tree_->SetModal(change_id, window->server_id());
+  tree_->SetModal(change_id, window->server_id(),
+                  window->GetWindow()->GetProperty(client::kModalKey));
   return true;
 }