Replace use of deprecated DOM.setStyleAttribute method (#13781)

This change is only a brain dead replacement of one specific method. In
some cases, there were some oddities in the surrounding code as well,
but these were left unresolved on purpose.

It should also be noted that DOM.setStyleAttribute just delegates to
element.getStyle().setProperty(), so any null references would have
caused problems already in the existing code.

Change-Id: I340122ac0767af9928076376f76e5bd2c5e19f9f