mash: Preliminary support for widget hit test masks

components/mus/public/cpp/tests/test_window_tree.h

Index: components/mus/public/cpp/tests/test_window_tree.h
diff --git a/components/mus/public/cpp/tests/test_window_tree.h b/components/mus/public/cpp/tests/test_window_tree.h
index 7e007bf8f23efe7f8fefde8d95a7930167bbfa08..2e14b72186b2651c3c7bf7dafee7ca272841d833 100644
--- a/components/mus/public/cpp/tests/test_window_tree.h
+++ b/components/mus/public/cpp/tests/test_window_tree.h
@@ -47,6 +47,7 @@ class TestWindowTree : public mojom::WindowTree {
       uint32_t window_id,
       mojo::InsetsPtr insets,
       mojo::Array<mojo::RectPtr> additional_client_areas) override;
+  void SetHitTestMask(uint32_t window_id, mojo::RectPtr mask) override;
   void SetWindowVisibility(uint32_t change_id,
                            uint32_t window_id,
                            bool visible) override;