When flutter/synchronization was first authored, we did not own fml (it was called fxl then). Now we do, so use a single spot for such utilities. The pipeline was meant to be a general purpose utility that was only ever used by the animator (it even has animator specific tracing), so move that to shell instead (where the animator resides).
Flow is a simple compositor based on Skia that the Flutter engine uses to cache
recoded paint commands and pixels generated from those recordings. Flow runs on
the GPU thread and uploads information to the GPU.