Add ComputeMac and ComputeSplitMacs methods to pref_hash_store.

components/user_prefs/tracked/pref_hash_store.h

Index: components/user_prefs/tracked/pref_hash_store.h
diff --git a/components/user_prefs/tracked/pref_hash_store.h b/components/user_prefs/tracked/pref_hash_store.h
index 2024a7d9ce79da0046a03efe515e9a0711979d87..3e5cc262ae719bf00d5ca3a33f8e5fb91f8bae8f 100644
--- a/components/user_prefs/tracked/pref_hash_store.h
+++ b/components/user_prefs/tracked/pref_hash_store.h
@@ -6,9 +6,12 @@
 #define COMPONENTS_PREFS_TRACKED_PREF_HASH_STORE_H_
 
 #include <memory>
+#include <string>
+
+#include "base/values.h"
+#include "components/user_prefs/tracked/pref_hash_store_transaction.h"
 
 class HashStoreContents;
-class PrefHashStoreTransaction;
 
 // Holds the configuration and implementation used to calculate and verify
 // preference MACs.
@@ -24,6 +27,21 @@ class PrefHashStore {
   // |storage| must outlive the returned transaction.
   virtual std::unique_ptr<PrefHashStoreTransaction> BeginTransaction(
       HashStoreContents* storage) = 0;
+
+  // Computes the MAC to be associated with |path| and |value| in this store.
+  // PrefHashStoreTransaction typically uses this internally but it's also
+  // exposed for users that want to compute MACs ahead of time for asynchronous
+  // operations.
+  virtual std::string ComputeMac(const std::string& path,
+                                 const base::Value* value) = 0;
+
+  // Computes the MAC to be associated with |path| and |split_values| in this
+  // store. PrefHashStoreTransaction typically uses this internally but it's
+  // also exposed for users that want to compute MACs ahead of time for
+  // asynchronous operations.
+  virtual std::unique_ptr<base::DictionaryValue> ComputeSplitMacs(
+      const std::string& path,
+      const base::DictionaryValue* split_values) = 0;
 };
 
 #endif  // COMPONENTS_PREFS_TRACKED_PREF_HASH_STORE_H_