aura-mus: add a drag representation image.

services/ui/ws/window_tree_client_unittest.cc

Index: services/ui/ws/window_tree_client_unittest.cc
diff --git a/services/ui/ws/window_tree_client_unittest.cc b/services/ui/ws/window_tree_client_unittest.cc
index eb2425f44e05fefe39d172a0763a905b1607ec69..bb7833bce6884447803fe172240cef6714de3860 100644
--- a/services/ui/ws/window_tree_client_unittest.cc
+++ b/services/ui/ws/window_tree_client_unittest.cc
@@ -479,6 +479,15 @@ class TestWindowTreeClient : public mojom::WindowTreeClient,
                                 bool janky) override {
     NOTIMPLEMENTED();
   }
+  void WmBuildDragImage(const gfx::Point& cursor_location,
+                        const SkBitmap& drag_image,
+                        const gfx::Vector2d& drag_image_offset,
+                        ui::mojom::DragEventSource source) override {}
+  void WmMoveDragImage(const gfx::Point& cursor_location,
+                       const WmMoveDragImageCallback& callback) override {
+    callback.Run();
+  }
+  void WmDestroyDragImage() override {}
   void WmPerformMoveLoop(uint32_t change_id,
                          uint32_t window_id,
                          mojom::MoveLoopSource source,