public function commit()
 {
     switch ($this->action) {
         case 'undo-edit-header':
         case 'edit-header':
             $this->workflow->updateLastModified($this->newRevision->getRevisionId());
             $this->storage->put($this->workflow, array());
             // 'discussion' workflow
             $this->storage->put($this->newRevision, array('workflow' => $this->workflow));
             // Reload $this->header for renderApi() after save
             $this->header = $this->newRevision;
             return array('header-revision-id' => $this->newRevision->getRevisionId());
         default:
             throw new InvalidActionException('Unrecognized commit action', 'invalid-action');
     }
 }