Inserting "<lf>\n" doesn't work. Prettify leaves the <lf> but
often inserts a <span> tag between <lf> and \n leaving a very
deep tag stack for the DOM to handle. This is really slow to
render and can cause mis-rendering.
Insert a space before LF. Most prettify styles will treat this
as the same as the LF, allowing the trailing space to be removed
before splitting by line.
Change-Id: I85d12c590a8d1bda1b1b66874a0dddb4628a8655
7e0aa0b417