The fix is to
- maintain the index of PasswordBuf at the start of IME
- maintain the old IME text
- remove the old IME text from PasswordBuf
/r=jfrancis, /sr=kin, /a=blizzard
git-svn-id: svn://10.0.0.236/trunk@96481 18797224-902f-48f8-a5cc-f745e15eee43