Remove SurfaceSequence from mus client code.

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 17bb37cee4344baa76ecb13af205008765b862c4..a8b7fa9c0bfad6e2525c76b762f4371430a00243 100644
--- a/ui/aura/test/mus/test_window_tree.cc
+++ b/ui/aura/test/mus/test_window_tree.cc
@@ -163,10 +163,6 @@ void TestWindowTree::AttachCompositorFrameSink(
     mojo::InterfaceRequest<cc::mojom::MojoCompositorFrameSink> surface,
     cc::mojom::MojoCompositorFrameSinkClientPtr client) {}
 
-void TestWindowTree::OnWindowSurfaceDetached(
-    uint32_t window_id,
-    const cc::SurfaceSequence& sequence) {}
-
 void TestWindowTree::AddWindow(uint32_t change_id,
                                uint32_t parent,
                                uint32_t child) {