Copy-paste regression

[Ezh]

Since Tb 66b(?) there is a major regression in copying tables to mail window.

FF copies it as a table:
ACANA Heritage 25 Dog Puppy & Junior 11,4kg 064992500115 45.5000 54.60 64.00 71.00 33
ACANA Heritage 25 Dog Puppy & Junior 17kg 064992500177 53.6500 64.38 93.00 98.00 5
ACANA Heritage 25 Dog Puppy & Junior 2kg 064992500207 14.8000 17.76 21.00 23.00 43

TB pastes it as a row:
ACANA Heritage 25 Dog Puppy & Junior 11,4kg 064992500115 45.5000 54.60 64.00 71.00 33 ACANA Heritage 25 Dog Puppy & Junior 17kg 064992500177 53.6500 64.38 93.00 98.00 5 ACANA Heritage 25 Dog Puppy & Junior 2kg 064992500207 14.8000 17.76 21.00 23.00 43

I filled a bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1555605