Fix scrolling performance issues in tree-view

[easyaspi314]

Part of fix for atom/atom#12949.

Forces Chromium to use the compositor to render scroll containers. This greatly decreases CPU usage when scrolling.

[simurai]

Tested this change and scrolling sometimes seems smoother, but not all the time. Kinda hard to tell. Also it seems that even though the .tree-view-scroller uses a compositor layer, it still needs painting. See how the paint count goes up when scrolling:

I think the problem is that the content inside a scrolling area needs to be clipped and therefore repainted. Not sure if it's possible to use overflow: auto without having to repaint? The editor uses compositor layers without repainting, but has to take care of moving the lines/tiles itself.