Factor out compressHTML method in Util and use it from bugSplit

VE output uses innerHTML directly without smart quoting for JSON attributes.
This produces a large diff, which makes it hard to detect actual content
changes.

This patch makes our smart quoting available from Util and uses it in bugSplit
for the editedHtml content.

Change-Id: Id5e628a8af3cacc515b37c7be01ce2f021635e20