aura-mus: add a drag representation image.

ui/aura/test/mus/test_window_tree.cc

Index: ui/aura/test/mus/test_window_tree.cc
diff --git a/ui/aura/test/mus/test_window_tree.cc b/ui/aura/test/mus/test_window_tree.cc
index 5082431b51f4ae1782271620f28c9c557e43c269..4ffe59121e93f9c824da6dd36ef3c68b300bce33 100644
--- a/ui/aura/test/mus/test_window_tree.cc
+++ b/ui/aura/test/mus/test_window_tree.cc
@@ -290,8 +290,12 @@ void TestWindowTree::GetCursorLocationMemory(
 void TestWindowTree::PerformDragDrop(
     uint32_t change_id,
     uint32_t source_window_id,
+    const gfx::Point& screen_location,
     const std::unordered_map<std::string, std::vector<uint8_t>>& drag_data,
-    uint32_t drag_operation) {
+    const SkBitmap& drag_image,
+    const gfx::Vector2d& drag_image_offset,
+    uint32_t drag_operation,
+    ui::mojom::DragEventSource source) {
   OnChangeReceived(change_id);
 }