a text in right alignment overflows at wrong position when being cut

Steps to Reproduce

1. run test case zss.test/alignment/1338-overflow-right-align.zul
2. type 'a' at D5 to cut the overflow text at F5

Current Result

the text exceeds the right cell border

Expected Result

the overflow text is totally inside a cell.

Debug Information

• this bug only happens in chrome (since 77), not in firefox