mus: Introduce AttachSurface to allow creating Surface prior to OnEmbed

components/mus/public/cpp/lib/window_tree_client_impl.cc

Index: components/mus/public/cpp/lib/window_tree_client_impl.cc
diff --git a/components/mus/public/cpp/lib/window_tree_client_impl.cc b/components/mus/public/cpp/lib/window_tree_client_impl.cc
index cf450d80e1eca01c393d8536021277df35492cb4..942a54017d19e173d772419461c49f566d09448d 100644
--- a/components/mus/public/cpp/lib/window_tree_client_impl.cc
+++ b/components/mus/public/cpp/lib/window_tree_client_impl.cc
@@ -263,13 +263,13 @@ void WindowTreeClientImpl::Embed(
   tree_->Embed(window_id, client.Pass(), policy_bitmask, callback);
 }
 
-void WindowTreeClientImpl::RequestSurface(
+void WindowTreeClientImpl::AttachToSurface(
     Id window_id,
     mojom::SurfaceType type,
     mojo::InterfaceRequest<mojom::Surface> surface,
     mojom::SurfaceClientPtr client) {
   DCHECK(tree_);
-  tree_->RequestSurface(window_id, type, surface.Pass(), client.Pass());
+  tree_->AttachToSurface(window_id, type, surface.Pass(), client.Pass());
 }
 
 void WindowTreeClientImpl::AddWindow(Window* window) {