R1:61057a9025f4

Fix filetree collapse

Summary: We need to nuke `has-drag-nav` too when the user presses "F" in Differential/Diffusion.

Test Plan: Pressed "F" in Differential.

Reviewers: zeeg, chad, btrahan

Reviewed By: chad

CC: aran

Differential Revision: https://secure.phabricator.com/D4457