Styling GWT FlexTable only with CSS

How do I style a GWT FlexTable using only CSS? The API mentions 开发者_C百科nothing about which CSS classes are available.

Aren't there any classes and do I have to set them myself?

I would for instance like to do styling on "th".

FlexTable (which extends HTMLTable) doesn't appear to apply any particular styles the cells it contains. There are two possible solutions:

1. Apply a style to the enclosing FlexTable and use descendent selectors (.myFlexTable th {}) to style the cells.
2. Use a CellFormatter to add your own style names to cells in the FlexTable.