Make WindowTree::SetModal() take the type.

services/ui/ws/modal_window_controller.cc

Index: services/ui/ws/modal_window_controller.cc
diff --git a/services/ui/ws/modal_window_controller.cc b/services/ui/ws/modal_window_controller.cc
index a07dc1f420ce93bdd92192f534ee0d063dc4b00c..ba75dd07baec126e4d368e53cbed8a9a86e9bee6 100644
--- a/services/ui/ws/modal_window_controller.cc
+++ b/services/ui/ws/modal_window_controller.cc
@@ -48,7 +48,7 @@ void ModalWindowController::AddSystemModalWindow(ServerWindow* window) {
   DCHECK(window);
   DCHECK(!base::ContainsValue(system_modal_windows_, window));
 
-  window->SetModal();
+  window->SetModal(ui::MODAL_TYPE_SYSTEM);
   system_modal_windows_.push_back(window);
   window_drawn_trackers_.insert(make_pair(
       window, base::MakeUnique<ServerWindowDrawnTracker>(window, this)));
@@ -80,6 +80,8 @@ bool ModalWindowController::IsWindowBlocked(const ServerWindow* window) const {
 
 const ServerWindow* ModalWindowController::GetTargetForWindow(
     const ServerWindow* window) const {
+  // TODO(moshayedi): crbug.com/697127. Handle windows which are modal to
+  // children of their transient parent.
   ServerWindow* system_modal_window = GetActiveSystemModalWindow();
   if (system_modal_window)
     return system_modal_window;