To improve wrapping behavior of rendered README files, don't use "PHUIDocumentView" in Diffusion

Summary:
See PHI1268. We currently do some weird width handling when rendering Diffusion readmes in a document directory view.

I think this came from D12330, which used `PHUIDocumentViewPro` to change the font, but we later reverted the font and were left with the `DocumentView`. Other changes after that modified `DocumentView` to have fixed-width behavior, but it doesn't make much sense here since the content panel is clearly rendered full-width.

Today, the `DocumentView` is a more structural element with methods like `setCurtain()`. Just get rid of it to simplify things, at least as a first step.

Test Plan:
Before:

{F6463493}

After:

{F6463492}

Reviewers: amckinley

Reviewed By: amckinley

Differential Revision: https://secure.phabricator.com/D20536

src/applications/diffusion/view/DiffusionReadmeView.php

@@ -75,7 +75,7 @@ final class DiffusionReadmeView extends DiffusionView {
         $engine = $markup_object->newMarkupEngine($markup_field);
 
         $readme_content = $content;
-        $class = null;
+        $class = 'ml';
         break;
       case 'rainbow':
         $content = id(new PhutilRainbowSyntaxHighlighter())
@@ -93,10 +93,12 @@ final class DiffusionReadmeView extends DiffusionView {
         break;
     }
 
-    $readme_content = phutil_tag_div($class, $readme_content);
-    $document = id(new PHUIDocumentView())
-      ->setFluid(true)
-      ->appendChild($readme_content);
+    $readme_content = phutil_tag(
+      'div',
+      array(
+        'class' => $class,
+      ),
+      $readme_content);
 
     $header = id(new PHUIHeaderView())
       ->setHeader($readme_name)
@@ -106,7 +108,7 @@ final class DiffusionReadmeView extends DiffusionView {
       ->setHeader($header)
       ->setBackground(PHUIObjectBoxView::BLUE_PROPERTY)
       ->addClass('diffusion-mobile-view')
-      ->appendChild($document)
+      ->appendChild($readme_content)
       ->addClass('diffusion-readme-view');
   }