Regression: rendering is wrong for http://maps.yandex.ru

There's a regression in the ES2 pipeline introduced in b86, reproducible on Linux and Mac:

Open http://maps.yandex.ru with WebLauncher or Browser. Wait a few seconds for navigation controls to load. You'll see a piece of the map drawn outside the map area (see also attached screenshot). Then if you move mouse over the links in the leftmost pane, they will disappear.

My investigation points at RT-26382 as the cause.