Today they are shared_ptr<Pipeline<PipelineDescriptor>>. This inflates the size of Command which are created hundreds of times per frame and also causes a synchronization when ~shared_ptr is called. The ContentContext should be keeping these alive and Command's are ephemeral so there is no need for it to have an owning reference to the pipeline.

This is even the case for runtime effects: https://github.com/flutter/engine/blob/main/impeller/entity/contents/content_context.cc#L572-L583

spawned from: #159177