Add best-effort/allow rollback flags on WorkItem.

chrome/installer/util/create_reg_key_work_item.h

Index: chrome/installer/util/create_reg_key_work_item.h
diff --git a/chrome/installer/util/create_reg_key_work_item.h b/chrome/installer/util/create_reg_key_work_item.h
index a55d941bbd4cbdac57ecbcb5b6485900d5285672..93b3a0eed83d48dfe95a235a12ca7d1d9bea11c3 100644
--- a/chrome/installer/util/create_reg_key_work_item.h
+++ b/chrome/installer/util/create_reg_key_work_item.h
@@ -18,10 +18,6 @@ class CreateRegKeyWorkItem : public WorkItem {
  public:
   ~CreateRegKeyWorkItem() override;
 
-  bool Do() override;
-
-  void Rollback() override;
-
  private:
   friend class WorkItem;
 
@@ -29,6 +25,10 @@ class CreateRegKeyWorkItem : public WorkItem {
                        const std::wstring& path,
                        REGSAM wow64_access);
 
+  // WorkItem:
+  bool DoImpl() override;
+  void RollbackImpl() override;
+
   // Initialize key_list_ by adding all paths of keys from predefined_root_
   // to path_. Returns true if key_list_ is non empty.
   bool InitKeyList();