function DraftEditorLeaf() {
	    _classCallCheck(this, DraftEditorLeaf);

	    return _possibleConstructorReturn(this, _React$Component.apply(this, arguments));
	  }
All leaf nodes in the editor are spans with single text nodes. Leaf
elements are styled based on the merging of an optional custom style map
and a default style map.

`DraftEditorLeaf` also provides a wrapper for calling into the imperative
DOM Selection API. In this way, top-level components can declaratively
maintain the selection state.