Label in problems panel is slightly clipped when using horizontal scrolling

[roblourens]

Testing #67275

• Enable horizontal scrolling
• Get a long error in the problems pane
• Scroll horizontally to see the end of the problem label
• Even when scrolled all the way to the right, it's slightly clipped

[joaomoreno]

@sandy081 This happens because you may have decorations coming up after the row was first rendered. If so, you should notify the tree that the row's width could have possibly changed, through the updateWidth(element) API.

[gregvanl]

Still see clipping as can't scroll far enough.

[sandy081]

@gregvanl Is it when you enable horizontal scrolling?

[sandy081]

Ignore my previous comment, I can repro it.