Introduce ColumnNames Enum

Release-Notes: skip
Change-Id: I4e8eec0781255f7d7b22ba18c3d24bc2f68ff170
diff --git a/polygerrit-ui/app/constants/constants.ts b/polygerrit-ui/app/constants/constants.ts
index 8cdd765..a0a6417 100644
--- a/polygerrit-ui/app/constants/constants.ts
+++ b/polygerrit-ui/app/constants/constants.ts
@@ -107,6 +107,20 @@
   SUCCESSFUL = 'SUCCESSFUL',
 }
 
+export enum ColumnNames {
+  SUBJECT = 'Subject',
+  // TODO(milutin) - remove once Submit Requirements are rolled out.
+  STATUS = 'Status',
+  OWNER = 'Owner',
+  REVIEWERS = 'Reviewers',
+  COMMENTS = 'Comments',
+  REPO = 'Repo',
+  BRANCH = 'Branch',
+  UPDATED = 'Updated',
+  SIZE = 'Size',
+  STATUS2 = ' Status ', // spaces to differentiate from old 'Status'
+}
+
 /**
  * @description Modes for gr-diff-cursor
  * The scroll behavior for the cursor. Values are 'never' and