Alternate fix for Firefox triple click selection

Summary:
Fixes T10905. This reverts D15823, which didn't work well for tasks with very long titles (the title would break as a block element).

This is slightly more magic but works with long titles.

Test Plan: Did everything from D15823, but also with long titles. Triple-click, wrapping, and mobile/device worked in Safari, Firefox and Chrome.

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T10905

Differential Revision: https://secure.phabricator.com/D15824