Add a view option to disable blame in Diffusion and fix some view transition bugs

Summary:
See PHI604. Ref T13130. Ref T13105. There's currently no way to turn blame off in Diffusion. Add a "Hide Blame" option to the "View Options" dropdown so it can be toggled off.

Also fix a couple of bugs around this: for example, if you loaded a Jupyter notebook and then switched to "Source" view, blame would incorrectly fail to activate because the original rendering of the "stage" used an asynchronous engine so `willRenderRef()` wasn't called to populate blame.

Test Plan:
  - Viewed a source file, toggled blame off/on, reloaded page to see state stick in URL.
  - Viewed a Jupyter notebook, toggled to "Source" view, saw blame.
  - Viewed stuff in Files (no blame UI options).
  - Tried to do some invalid stuff like toggle blame on a non-blame engine (options disable properly).

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13130, T13105

Differential Revision: https://secure.phabricator.com/D19414

src/applications/files/document/PhabricatorDocumentEngine.php

@@ -7,6 +7,7 @@ abstract class PhabricatorDocumentEngine
   private $highlightedLines = array();
   private $encodingConfiguration;
   private $highlightingConfiguration;
+  private $blameConfiguration = true;
 
   final public function setViewer(PhabricatorUser $viewer) {
     $this->viewer = $viewer;
@@ -60,6 +61,19 @@ abstract class PhabricatorDocumentEngine
     return $this->highlightingConfiguration;
   }
 
+  final public function setBlameConfiguration($blame_configuration) {
+    $this->blameConfiguration = $blame_configuration;
+    return $this;
+  }
+
+  final public function getBlameConfiguration() {
+    return $this->blameConfiguration;
+  }
+
+  final protected function getBlameEnabled() {
+    return $this->blameConfiguration;
+  }
+
   public function shouldRenderAsync(PhabricatorDocumentRef $ref) {
     return false;
   }