Whatever you type in text field like search field in google... every 2 byte character especially Korean is being inputed twice or more. Also while your typing Korean, if you try to delete a character by pressing 'delete(backspace)' key. Webkit turns you to previous web page.
This sounds very much like a duplicate of bug 12531.
The duplication is covered by bug 12531, but backspace problem is not.
Committed revision 19579.