Fix position of LoadingMessage in LoadingIndicator

[rkaneriya]

Current behavior:

• when LoadingIndicator wraps around an element that scrolls, the LoadingMessage box is centered in the middle of that element. This means that it can sometimes be hidden from view if the scrolling area is very long.

Suggested behavior:

• fix the position of the LoadingMessage box to the center of the visible area of the wrapped element

Suggested fix:

• position: fixed; top: 50% on the LoadingMessage element

[jondlm]

I've seen this issue in some places as well. I'm not sure position: fixed is quite right though, I think that would cause the indicator to position itself to the window, which is a pretty different behavior.