Prevent transformed ops from merging in the first place

bug:8649215

Previously we prevented ops with non-translate transforms from
merging, but missed the case of the first op in a merging batch
containing a non-translate transform.

This fulfills the assumption of drawText's non-immediate mode that
merged ops will have pure translate transforms.

Change-Id: I6f6db341aff3f7e84e74b4c3ccf970d585a2db1a