Scroll position not updated when editor size change

[lishid]

Steps to repro

• Go to https://codemirror.net/
• Run console code editor.setValue(new Array(100).fill('test').join('\n'));
• Scroll editor down.
• Run console code editor.setValue('test');
• Run console code editor.setValue(new Array(100).fill('test').join('\n'));

Expected results

Editor fully scrolled to the top

Observed results

Scroll bar shows editor scrolled to the bottom, while text seems to be scrolled to the top.

Notes

Could be a recent regression

Screencap

[marijnh]

This doesn't happen on Firefox. Seems Chrome somehow 'smartly' restores the scrollbar position here, which isn't a good idea. Attached patch should fix it.