mus: Introduce AttachSurface to allow creating Surface prior to OnEmbed

components/mus/ws/window_tree_impl.h

Index: components/mus/ws/window_tree_impl.h
diff --git a/components/mus/ws/window_tree_impl.h b/components/mus/ws/window_tree_impl.h
index babe1d7c3eea264a31b66df216c249db0f0ecb95..e349c71cbcefd6106adb3037010858a603db38b2 100644
--- a/components/mus/ws/window_tree_impl.h
+++ b/components/mus/ws/window_tree_impl.h
@@ -226,10 +226,10 @@ class WindowTreeImpl : public mojom::WindowTree, public AccessPolicyDelegate {
                          Id window_id,
                          const mojo::String& name,
                          mojo::Array<uint8_t> value) override;
-  void RequestSurface(Id window_id,
-                      mojom::SurfaceType type,
-                      mojo::InterfaceRequest<mojom::Surface> surface,
-                      mojom::SurfaceClientPtr client) override;
+  void AttachSurface(Id window_id,
+                     mojom::SurfaceType type,
+                     mojo::InterfaceRequest<mojom::Surface> surface,
+                     mojom::SurfaceClientPtr client) override;
   void Embed(Id transport_window_id,
              mojom::WindowTreeClientPtr client,
              uint32_t policy_bitmask,