aura-mus: Implement Deactivate().

services/ui/ws/test_utils.h

Index: services/ui/ws/test_utils.h
diff --git a/services/ui/ws/test_utils.h b/services/ui/ws/test_utils.h
index edf76fffacf24ecc0deab5f6f37fe14ef5fb2ec4..60cb637e25bcff280ab2009757997b7cd7385726 100644
--- a/services/ui/ws/test_utils.h
+++ b/services/ui/ws/test_utils.h
@@ -357,6 +357,7 @@ class TestWindowManager : public mojom::WindowManager {
                          mojom::MoveLoopSource source,
                          const gfx::Point& cursor_location) override;
   void WmCancelMoveLoop(uint32_t window_id) override;
+  void WmDeactivateWindow(uint32_t window_id) override;
   void OnAccelerator(uint32_t ack_id,
                      uint32_t accelerator_id,
                      std::unique_ptr<ui::Event> event) override;