R1:6bc5ed39a24d

Fix two tokenizer issues on iDevices

Summary: Fixes T3853. See inline comments for details.

Test Plan: Using iOS simulator, mashed the right hand side of tokenizers.

Reviewers: chad, btrahan

Reviewed By: chad

CC: aran

Maniphest Tasks: T3853

Differential Revision: https://secure.phabricator.com/D7049