Always show "X requested review" in mail to stop some undraft mail from being dropped

Summary: Ref T13035. See that task for a description of the issue.

Test Plan:
  - Enabled prototypes.
  - Disabled all Herald rules that trigger Harbormaster builds.
  - Created a new revision.
  - Before patch: initial review request email was dropped.
  - After patch: initial review request email is sent.

Reviewers: amckinley

Reviewed By: amckinley

Maniphest Tasks: T13035

Differential Revision: https://secure.phabricator.com/D18851

src/applications/differential/storage/DifferentialTransaction.php

@@ -111,6 +111,12 @@ final class DifferentialTransaction
         // Don't hide the initial "X added reviewers: ..." transaction during
         // object creation from mail. See T12118 and PHI54.
         return false;
+      case DifferentialRevisionRequestReviewTransaction::TRANSACTIONTYPE:
+        // Don't hide the initial "X requested review: ..." transaction from
+        // mail even when it occurs during creation. We need this transaction
+        // to survive so we'll generate mail when revisions immediately leave
+        // the draft state. See T13035 for discussion.
+        return false;
     }
 
     return parent::shouldHideForMail($xactions);