Update {virtual,override} to follow C++11 style in chrome.

chrome/installer/util/delete_reg_key_work_item.h

Index: chrome/installer/util/delete_reg_key_work_item.h
diff --git a/chrome/installer/util/delete_reg_key_work_item.h b/chrome/installer/util/delete_reg_key_work_item.h
index 0fc11f6896422e219d4be5edab76100d316f91f4..54cddbace1f0590a09dadb6697fd37a6cf1745ae 100644
--- a/chrome/installer/util/delete_reg_key_work_item.h
+++ b/chrome/installer/util/delete_reg_key_work_item.h
@@ -21,11 +21,11 @@ class RegistryKeyBackup;
 // the key and its subkeys take on their default security descriptors.
 class DeleteRegKeyWorkItem : public WorkItem {
  public:
-  virtual ~DeleteRegKeyWorkItem();
+  ~DeleteRegKeyWorkItem() override;
 
-  virtual bool Do() override;
+  bool Do() override;
 
-  virtual void Rollback() override;
+  void Rollback() override;
 
  private:
   friend class WorkItem;