[v4] Content scrolls via mousewheel even when it fits in view

[njx]

Reproduces on both Mac and Win in Chrome 33.

1. Open http://codemirror.net/4/demo/theme.html
2. Move the mouse over the editor and do a touch scroll or mousewheel scroll

Result: content scrolls upwards a little bit even though it fully fits in the window. Note also that no scrollbars are visible.

[marijnh]

Attached patch should help.

[njx]

Yes, that seems to fix it. Thanks.