Revision 357045

Bugzilla #37875:
Some content inside a table-header may not have been renderered on pages n > 1 in certain conditions.
LineLM kept state between calls to addAreas which can have ugly side-effects in case of table-headers, for example, where the same positions are rendered more than once. I don't know why the bug only manifests if there's an overflow in the second line of the table-header in the test case.