mus: Implement interwindow drag and drop

services/ui/ws/window_manager_state.cc

Index: services/ui/ws/window_manager_state.cc
diff --git a/services/ui/ws/window_manager_state.cc b/services/ui/ws/window_manager_state.cc
index 224207202adc95319a720e7aab3b604d6d27c146..5c9ec89b7287a516f7f7d3c408800ac7b66c3501 100644
--- a/services/ui/ws/window_manager_state.cc
+++ b/services/ui/ws/window_manager_state.cc
@@ -154,6 +154,17 @@ void WindowManagerState::ReleaseCaptureBlockedByAnyModalWindow() {
   event_dispatcher_.ReleaseCaptureBlockedByAnyModalWindow();
 }
 
+void WindowManagerState::SetDragDropSourceWindow(
+    uint32_t change_id,
+    mojo::Map<mojo::String, mojo::Array<uint8_t>> drag_data,
+    uint32_t drag_operation,
+    WindowTree* window_tree,
+    ServerWindow* capture_window) {
+  event_dispatcher_.SetDragDropSourceWindow(
+      change_id, window_tree, capture_window, std::move(drag_data),
+      drag_operation);
+}
+
 void WindowManagerState::AddSystemModalWindow(ServerWindow* window) {
   DCHECK(!window->transient_parent());
   event_dispatcher_.AddSystemModalWindow(window);