Refactor PrefHashStore's BeginTransaction to take a rawptr

components/user_prefs/tracked/pref_hash_store.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_PREFS_TRACKED_PREF_HASH_STORE_H_
 #define COMPONENTS_PREFS_TRACKED_PREF_HASH_STORE_H_
 
 #include <memory>
 
 class HashStoreContents;
 class PrefHashStoreTransaction;
 
 // Holds the configuration and implementation used to calculate and verify
 // preference MACs.
 // TODO(gab): Rename this class as it is no longer a store.
 class PrefHashStore {
  public:
   virtual ~PrefHashStore() {}
 
   // Returns a PrefHashStoreTransaction which can be used to perform a series
   // of operations on the hash store. |storage| MAY be used as the backing store
   // depending on the implementation. Therefore the HashStoreContents used for
   // related transactions should correspond to the same underlying data store.
+  // Does not own the HashStoreContents; callers must ensure transaction must
+  // not outlive |storage|.

[gab, 2016/09/01 20:31:50]

Raw pointer in Chromium always implies lack of ownership, last sentence could
simply be:

// |storage| must outlive the returned transaction.

[proberge, 2016/09/06 19:24:10]

Done.

   virtual std::unique_ptr<PrefHashStoreTransaction> BeginTransaction(
-      std::unique_ptr<HashStoreContents> storage) = 0;
+      HashStoreContents* storage) = 0;
 };
 
 #endif  // COMPONENTS_PREFS_TRACKED_PREF_HASH_STORE_H_