Reland: mus: Enable system modal windows

components/mus/ws/window_manager_state.cc

Index: components/mus/ws/window_manager_state.cc
diff --git a/components/mus/ws/window_manager_state.cc b/components/mus/ws/window_manager_state.cc
index c81bb8cb86b78b4d1ccfc2e6e0649a9e30cc96f3..8d50d55c44f998e3eed9fe5342d63628b33ae78f 100644
--- a/components/mus/ws/window_manager_state.cc
+++ b/components/mus/ws/window_manager_state.cc
@@ -128,8 +128,9 @@ bool WindowManagerState::SetCapture(ServerWindow* window,
 void WindowManagerState::ReleaseCaptureBlockedByModalWindow(
     const ServerWindow* modal_window) {
   if (!capture_window() || !modal_window->is_modal() ||
-      !modal_window->IsDrawn())
+      !modal_window->IsDrawn()) {
     return;
+  }
 
   if (modal_window->transient_parent() &&
       !modal_window->transient_parent()->Contains(capture_window())) {
@@ -140,12 +141,25 @@ void WindowManagerState::ReleaseCaptureBlockedByModalWindow(
 }
 
 void WindowManagerState::ReleaseCaptureBlockedByAnyModalWindow() {
-  if (!capture_window() || !capture_window()->IsBlockedByModalWindow())
+  if (!capture_window())
+    return;
+
+  bool has_system_modal =
+      system_modal_window() && system_modal_window()->IsDrawn();
+
+  if (!has_system_modal && !capture_window()->IsBlockedByModalWindow())
     return;
 
   SetCapture(nullptr, false);
 }
 
+bool WindowManagerState::SetSystemModalWindow(ServerWindow* window) {
+  DCHECK(!window->transient_parent());
+  if (system_modal_window() == window)
+    return true;
+  return event_dispatcher_.SetSystemModalWindow(window);
+}
+
 mojom::DisplayPtr WindowManagerState::ToMojomDisplay() const {
   mojom::DisplayPtr display_ptr = display_->ToMojomDisplay();
   // TODO(sky): set work area.