test(messageviewerplugins): Adopt changes from ObjectTreeParser

Authored by knauss on Sep 11 2019, 7:19 AM.

Description

test(messageviewerplugins): Adopt changes from ObjectTreeParser

Summary:
MimeTreeParser::ObjectTreeParser is now completely agnositc of
rendering. That means we have to trigger the rendering step on our own.

Reviewers: KDE PIM, dvratil

Subscribers: kde-pim

Tags: KDE PIM

Differential Revision: https://phabricator.kde.org/D23864