mus: Server-side implementation of modal windows

components/mus/ws/window_tree_impl.cc

Index: components/mus/ws/window_tree_impl.cc
diff --git a/components/mus/ws/window_tree_impl.cc b/components/mus/ws/window_tree_impl.cc
index f144d3ad60930d06e3a3a554adb700ffdf16a8fb..eb8222dff81b7abf8f975b360ef255d533c520eb 100644
--- a/components/mus/ws/window_tree_impl.cc
+++ b/components/mus/ws/window_tree_impl.cc
@@ -228,6 +228,15 @@ bool WindowTreeImpl::AddTransientWindow(
   return false;
 }
 
+bool WindowTreeImpl::SetAsModal(const ClientWindowId& window_id) {
+  ServerWindow* window = GetWindowByClientId(window_id);
+  if (window && access_policy_->CanSetAsModal(window)) {
+    window->SetAsModal();
+    return true;
+  }
+  return false;
+}
+
 std::vector<const ServerWindow*> WindowTreeImpl::GetWindowTree(
     const ClientWindowId& window_id) const {
   const ServerWindow* window = GetWindowByClientId(window_id);
@@ -980,6 +989,10 @@ void WindowTreeImpl::RemoveTransientWindowFromParent(uint32_t change_id,
   client_->OnChangeCompleted(change_id, success);
 }
 
+void WindowTreeImpl::SetAsModal(uint32_t change_id, Id window_id) {
+  client_->OnChangeCompleted(change_id, SetAsModal(ClientWindowId(window_id)));
+}
+
 void WindowTreeImpl::ReorderWindow(uint32_t change_id,
                                    Id window_id,
                                    Id relative_window_id,