'path-frontpage' class isn't applied when previewing a node

I've stumbled upon this issue, when tried to preview a node, that is set to be frontpage.

Steps:
1. Have unique CSS style assigned to `path-frontpage` class. Ex:

.path-frontpage {
  background-color: blue;
}

2. Create a node, so you have a URL. Ex: /node/1
3. Set URL to be a frontpage.
4. Edit and preview the node.

Expectation:
Since this node is set to be a frontpage, any frontpage related styling must be applied, otherwise, the preview is deceptive.

Current behavior:
Class `path-frontpage` isn't assigned to a body tag during node preview. Hence no styling is applied.