Bug on selecting/editing cells with big tables

[NikitaArgov]

If you scroll to the bottom of big table (>1000 rows, better with 10000 rows), it will be impossible to select cells from top of visible area (it makes "page up" instead of selecting).

If you scroll back to the top, the error disappears. If you scroll to 50%, the area of this effect is smaller.

The bug can be easily reproduced by increasing the number of rows in /sample/index2.html