Preserve linebreaks again in Summary / Test Plan for revisions

Summary:
I pulled these into the property list recently, which made them more consistent, but that dropped "preserve linebreaks". Since these usually come from the CLI, render with linebreaks preserved.

@csilvers, you'll need to `bin/cache purge --purge-remarkup` after this if you want to fix existing revisions.

Test Plan: Made a revision with some poetry, saw poetry preserved.

Reviewers: btrahan, csilvers

Reviewed By: btrahan

CC: csilvers, aran

Differential Revision: https://secure.phabricator.com/D7464

src/applications/differential/view/DifferentialRevisionDetailView.php

@@ -118,8 +118,9 @@ final class DifferentialRevisionDetailView extends AphrontView {
       $properties->addSectionHeader(pht('Summary'));
       $properties->addTextContent(
         PhabricatorMarkupEngine::renderOneObject(
-          id(new PhabricatorMarkupOneOff())->setContent(
-            $revision->getSummary()),
+          id(new PhabricatorMarkupOneOff())
+            ->setPreserveLinebreaks(true)
+            ->setContent($revision->getSummary()),
           'default',
           $user));
     }
@@ -128,8 +129,9 @@ final class DifferentialRevisionDetailView extends AphrontView {
       $properties->addSectionHeader(pht('Test Plan'));
       $properties->addTextContent(
         PhabricatorMarkupEngine::renderOneObject(
-          id(new PhabricatorMarkupOneOff())->setContent(
-            $revision->getTestPlan()),
+          id(new PhabricatorMarkupOneOff())
+            ->setPreserveLinebreaks(true)
+            ->setContent($revision->getTestPlan()),
           'default',
           $user));
     }