Windows: Avoid assertion when entering zero-length text in the default JavaScript prompt dialog (issue #862).

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk@1045 5089003a-bbd8-11dd-ad1f-f1f9622dbc98
Windows: Add default implementation for JavaScript prompt dialog (issue #861).

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk@1049 5089003a-bbd8-11dd-ad1f-f1f9622dbc98