Add ComputeMac and ComputeSplitMacs methods to pref_hash_store.

components/user_prefs/tracked/pref_hash_store_impl.h

Index: components/user_prefs/tracked/pref_hash_store_impl.h
diff --git a/components/user_prefs/tracked/pref_hash_store_impl.h b/components/user_prefs/tracked/pref_hash_store_impl.h
index a532cd2011b715f07b3f3263b4583fd196b38cad..1b5682eed4e83df46a039b50352e77da565756ff 100644
--- a/components/user_prefs/tracked/pref_hash_store_impl.h
+++ b/components/user_prefs/tracked/pref_hash_store_impl.h
@@ -5,17 +5,11 @@
 #ifndef COMPONENTS_USER_PREFS_TRACKED_PREF_HASH_STORE_IMPL_H_
 #define COMPONENTS_USER_PREFS_TRACKED_PREF_HASH_STORE_IMPL_H_
 
-#include <memory>
-#include <string>
-
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "components/user_prefs/tracked/pref_hash_calculator.h"
 #include "components/user_prefs/tracked/pref_hash_store.h"
 
-class HashStoreContents;
-class PrefHashStoreTransaction;
-
 // Implements PrefHashStoreImpl by storing preference hashes in a
 // HashStoreContents.
 class PrefHashStoreImpl : public PrefHashStore {
@@ -49,6 +43,12 @@ class PrefHashStoreImpl : public PrefHashStore {
   std::unique_ptr<PrefHashStoreTransaction> BeginTransaction(
       HashStoreContents* storage) override;
 
+  std::string ComputeMac(const std::string& path,
+                         const base::Value* new_value) override;
+  std::unique_ptr<base::DictionaryValue> ComputeSplitMacs(
+      const std::string& path,
+      const base::DictionaryValue* split_values) override;
+
  private:
   class PrefHashStoreTransactionImpl;