The implementation of these methods was updated from direct java integer
arithmetic in 885ddb167e.
In this change, `RoundingMode.FLOOR` was used to try and maintain
compatibility with java integer division. This was incorrect, because
java integer division uses `DOWN` (i.e. towards zero), rather than
`FLOOR` (i.e. towards negative infinity) semantics.
This change fixes the compatibility.
The dump file changes in this CL relate to tests that exercise edit
list behaviour. This involves manipulating negative timestamps, which
explains why they are impacted by this change.
PiperOrigin-RevId: 684013175
2c46cea088