Add best-effort/allow rollback flags on WorkItem.

chrome/installer/util/delete_reg_value_work_item.h

Index: chrome/installer/util/delete_reg_value_work_item.h
diff --git a/chrome/installer/util/delete_reg_value_work_item.h b/chrome/installer/util/delete_reg_value_work_item.h
index f1bd50a9b7123c96618b16f03edf63597d4b4380..440780db422827f12f3b606d09ec7f1555ee8b33 100644
--- a/chrome/installer/util/delete_reg_value_work_item.h
+++ b/chrome/installer/util/delete_reg_value_work_item.h
@@ -18,10 +18,6 @@ class DeleteRegValueWorkItem : public WorkItem {
  public:
   ~DeleteRegValueWorkItem() override;
 
-  bool Do() override;
-
-  void Rollback() override;
-
  private:
   friend class WorkItem;
 
@@ -43,6 +39,10 @@ class DeleteRegValueWorkItem : public WorkItem {
                          REGSAM wow64_acccess,
                          const std::wstring& value_name);
 
+  // WorkItem:
+  bool DoImpl() override;
+  void RollbackImpl() override;
+
   // Root key of the target key under which the value is set. The root key can
   // only be one of the predefined keys on Windows.
   HKEY predefined_root_;