Add best-effort/allow rollback flags on WorkItem.

chrome/installer/util/move_tree_work_item.h

Index: chrome/installer/util/move_tree_work_item.h
diff --git a/chrome/installer/util/move_tree_work_item.h b/chrome/installer/util/move_tree_work_item.h
index eea5cdabf9be562de42d42a4922997051f5c4da2..38383d4927a6dfa9acc375d4db2b663a75b13036 100644
--- a/chrome/installer/util/move_tree_work_item.h
+++ b/chrome/installer/util/move_tree_work_item.h
@@ -22,10 +22,6 @@ class MoveTreeWorkItem : public WorkItem {
  public:
   ~MoveTreeWorkItem() override;
 
-  bool Do() override;
-
-  void Rollback() override;
-
  private:
   friend class WorkItem;
   FRIEND_TEST_ALL_PREFIXES(MoveTreeWorkItemTest,
@@ -47,6 +43,10 @@ class MoveTreeWorkItem : public WorkItem {
                    const base::FilePath& temp_dir,
                    MoveTreeOption duplicate_option);
 
+  // WorkItem:
+  bool DoImpl() override;
+  void RollbackImpl() override;
+
   // Source path to move files from.
   base::FilePath source_path_;