What happened:
One of my projects broke, fairly catastrophically, after updating to dask==2.26.0. In particular, chunk sizes of arrays get mangled in completely mysterious ways. This does not happen when using dask<=2.25.0.

What you expected to happen:
I would have expected no change to existing chunking behaviour.

Minimal Complete Verifiable Example:
This issue aims to get more dask-knowledgeable eyes on this issue on xarray.

Environment:

• Dask version: 2.26.0
• Python version: 3.6.9
• Operating System: Pop!_OS 18.04 LTS
• Install method (conda, pip, source): pip