Step to reproduce :
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1) Run the attached testcase.
2) Copy the content of the attached testcase and paste inside the multiline textbox.
3) Click on the multiline checkbox, so that textbox can switch to single line textbox.
4) Click on the multiline checkbox, so that textbox can switch back to multi line textbox.
Observe that content of the textbox is not seen. If you see the same then the bug is reproduce.