When a draft's builds fail and it demotes to "Changes Planned + Draft", notify the author (only) via email

Summary:
Depends on D19288. Ref T13110. In addition to kicking revisions back to "Changes Planned" when builds fail, notify the author that they need to fix their awful garbage change.

(The actual email could be more useful than it currently is.)

Test Plan: Created a revision with failing remote builds, saw email about the problem generate.

Maniphest Tasks: T13110

Differential Revision: https://secure.phabricator.com/D19289

src/applications/differential/editor/DifferentialTransactionEditor.php

@@ -11,6 +11,7 @@ final class DifferentialTransactionEditor
   private $affectedPaths;
   private $firstBroadcast = false;
   private $wasBroadcasting;
+  private $isDraftDemotion;
 
   public function getEditorApplicationClass() {
     return 'PhabricatorDifferentialApplication';
@@ -134,6 +135,11 @@ final class DifferentialTransactionEditor
           // as "Commented" later. This should get cleaner after T10967.
           $this->hasReviewTransaction = true;
           break;
+        case DifferentialRevisionPlanChangesTransaction::TRANSACTIONTYPE:
+          if ($xaction->getMetadataValue('draft.demote')) {
+            $this->isDraftDemotion = true;
+          }
+          break;
       }
     }
 
@@ -497,15 +503,11 @@ final class DifferentialTransactionEditor
   protected function shouldSendMail(
     PhabricatorLiskDAO $object,
     array $xactions) {
-
-    if (!$object->getShouldBroadcast()) {
-      return false;
-    }
-
     return true;
   }
 
   protected function getMailTo(PhabricatorLiskDAO $object) {
+    if ($object->getShouldBroadcast()) {
       $this->requireReviewers($object);
 
       $phids = array();
@@ -520,6 +522,25 @@ final class DifferentialTransactionEditor
       return $phids;
     }
 
+    // If we're demoting a draft after a build failure, just notify the author.
+    if ($this->isDraftDemotion) {
+      $author_phid = $object->getAuthorPHID();
+      return array(
+        $author_phid,
+      );
+    }
+
+    return array();
+  }
+
+  protected function getMailCC(PhabricatorLiskDAO $object) {
+    if (!$object->getShouldBroadcast()) {
+      return array();
+    }
+
+    return parent::getMailCC($object);
+  }
+
   protected function newMailUnexpandablePHIDs(PhabricatorLiskDAO $object) {
     $this->requireReviewers($object);
 
@@ -1408,12 +1429,14 @@ final class DifferentialTransactionEditor
     return array(
       'changedPriorToCommitURI' => $this->changedPriorToCommitURI,
       'firstBroadcast' => $this->firstBroadcast,
+      'isDraftDemotion' => $this->isDraftDemotion,
     );
   }
 
   protected function loadCustomWorkerState(array $state) {
     $this->changedPriorToCommitURI = idx($state, 'changedPriorToCommitURI');
     $this->firstBroadcast = idx($state, 'firstBroadcast');
+    $this->isDraftDemotion = idx($state, 'isDraftDemotion');
     return $this;
   }