* Add tab bar theme.

* Add tab bar theme.

* Add tests, pass context to getters.

* update goldens from linux box

* update goldens from linux box

* Added new golden test, addressed comments

* override hashCode and == in TabBarTheme

* Fix comment typos

* Addressed Hans' comments.

* Formatting changes

* [TabBarTheme] Fixed spacing

* [TabBarTheme] Update goldens version to latest commit