Fix tab-focus of Tokenizers

Summary: Fixes T3140. Previously, we added the highlight class only on explicit events, but not on actual focus events (e.g., via tab).

Test Plan: Tabbed into a tokenizer. Clicked a tokenizer. Tabbed out of a tokenizer. Clicked out of a tokenizer. Shift-tabbed out of a tokenizer. Verified highlight state was always correct.

Reviewers: chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T3140

Differential Revision: https://secure.phabricator.com/D5891