Added CSS to existing selector: preserve whitespace in review mode

In review mode, whitespace was not preserved: newlines were
being displayed as single spaces, messing up messages.

Code courtesy: Jesús Martínez Novo
Bug: 60198
Change-Id: I11190fd1b0970277fc57ff95a43efaf3ece585a9
Merge "Added CSS to existing selector: preserve whitespace in review mode"