Remove some linked_ptr c/b/extension

chrome/browser/extensions/api/storage/managed_value_store_cache.h

Index: chrome/browser/extensions/api/storage/managed_value_store_cache.h
diff --git a/chrome/browser/extensions/api/storage/managed_value_store_cache.h b/chrome/browser/extensions/api/storage/managed_value_store_cache.h
index f0d5beffa233c29076d0c5fa94ca3a76ec5cd63e..3545ae870bb1522e6392015bbfbba4323f3c6d03 100644
--- a/chrome/browser/extensions/api/storage/managed_value_store_cache.h
+++ b/chrome/browser/extensions/api/storage/managed_value_store_cache.h
@@ -12,7 +12,6 @@
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
-#include "base/memory/linked_ptr.h"
 #include "base/memory/ref_counted.h"
 #include "components/policy/core/common/policy_service.h"
 #include "extensions/browser/api/storage/settings_observer.h"
@@ -51,10 +50,6 @@ class ManagedValueStoreCache : public ValueStoreCache,
  private:
   class ExtensionTracker;
 
-  // Maps an extension ID to its PolicyValueStoreMap.
-  typedef std::map<std::string, linked_ptr<PolicyValueStore> >
-      PolicyValueStoreMap;
-
   // ValueStoreCache implementation:
   void ShutdownOnUI() override;
   void RunWithValueStoreForExtension(
@@ -96,7 +91,7 @@ class ManagedValueStoreCache : public ValueStoreCache,
 
   // All the PolicyValueStores live on the FILE thread, and |store_map_| can be
   // accessed only on the FILE thread as well.
-  PolicyValueStoreMap store_map_;
+  std::map<std::string, std::unique_ptr<PolicyValueStore>> store_map_;
 
   DISALLOW_COPY_AND_ASSIGN(ManagedValueStoreCache);
 };