Routes WindowManager functionality through the view manager

This is an ugly hack, but necessary until we have the ability to have
message ordering for multiple pipes.

BUG=460621
R=msw@chromium.org

Review URL: https://codereview.chromium.org/954273002
diff --git a/services/view_manager/view_manager_service_impl.h b/services/view_manager/view_manager_service_impl.h
index a315178..e92e1fa 100644
--- a/services/view_manager/view_manager_service_impl.h
+++ b/services/view_manager/view_manager_service_impl.h
@@ -210,6 +210,9 @@
   void Embed(mojo::Id transport_view_id,
              mojo::ViewManagerClientPtr client,
              const mojo::Callback<void(bool)>& callback) override;
+  void PerformAction(mojo::Id transport_view_id,
+                     const mojo::String& action,
+                     const mojo::Callback<void(bool)>& callback) override;
 
   // AccessPolicyDelegate:
   bool IsRootForAccessPolicy(const ViewId& id) const override;