Remove some linked_ptr c/b/extension

chrome/browser/extensions/extension_action_manager.h

Index: chrome/browser/extensions/extension_action_manager.h
diff --git a/chrome/browser/extensions/extension_action_manager.h b/chrome/browser/extensions/extension_action_manager.h
index 3e6569687430435edc373b1eebeb4f3173f5a3b7..6693d8173487a815d2ce0799daed70ea942d6b9c 100644
--- a/chrome/browser/extensions/extension_action_manager.h
+++ b/chrome/browser/extensions/extension_action_manager.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_ACTION_MANAGER_H_
 
 #include <map>
+#include <memory>
 #include <string>
 
 #include "base/scoped_observer.h"
@@ -71,7 +72,8 @@ class ExtensionActionManager : public KeyedService,
   // ExtensionAction is first requested, and the entries are removed when the
   // extension is unloaded.  Not every extension has a page action or browser
   // action.
-  typedef std::map<std::string, linked_ptr<ExtensionAction> > ExtIdToActionMap;
+  using ExtIdToActionMap =
+      std::map<std::string, std::unique_ptr<ExtensionAction>>;
   mutable ExtIdToActionMap page_actions_;
   mutable ExtIdToActionMap browser_actions_;
   mutable ExtIdToActionMap system_indicators_;