Hygiene: Consolidate the overlay-header h2 rules

Change-Id: Ie2c5a751b0b0c78bcb9dfd7f1d77e5f87acee7b9
Hygiene: Consolidate beta thumb styles in one place

Also wrap in .content selector to match what is in common.less and
thus make sure that it actually overrides in all cases.

Change-Id: Ic663165baf9b92d0149dc3aa007d8f153a94a3d0
Merge "Hygiene: Consolidate the overlay-header h2 rules"
Merge "Hygiene: Consolidate beta thumb styles in one place"