Most of the code in GpuProcessTransportFactory belongs in the Viz service including creation of the viz::Display, the BeginFrameSource, and the
OutputSurface.

We should create a new DisplayProvider that moves that functionality
out of GpuProcessTransportFactory. That DisplayProvider is then passed
into FrameSinkManagerImpl's construction.

The end state of this work is DirectLayerTreeFrameSink goes away, and instead content uses RootCompositorFrameSinkImpl for UI. Initially,
we may not use a Mojo MessagePipe but we will still use raw pointers
to mojo interfaces in UI.