R1:f910c379ce04

Modify whitespace default implementation

Summary:
Take Tuomas's first diff. Sorry, my bad on diff feedback.

Test Plan:
Load D240353 without any options and make sure 'ignore-trailing'
selected.

Reviewed By: tuomaspelkonen
Reviewers: tuomaspelkonen
CC: epriestley, aran, tuomaspelkonen
Differential Revision: 172