[Sync] Add ability to save/restore Nigori to SyncEncryptionHandlerImpl

sync/internal_api/sync_encryption_handler_impl.h

Index: sync/internal_api/sync_encryption_handler_impl.h
diff --git a/sync/internal_api/sync_encryption_handler_impl.h b/sync/internal_api/sync_encryption_handler_impl.h
index 79f43f2f237ac2c02d1c264a99e0c19653c03aaa..e5f406fcd15e2782f370907baf56ac3a9b060797 100644
--- a/sync/internal_api/sync_encryption_handler_impl.h
+++ b/sync/internal_api/sync_encryption_handler_impl.h
@@ -88,6 +88,11 @@ class SYNC_EXPORT_PRIVATE SyncEncryptionHandlerImpl
   base::Time migration_time() const;
   base::Time custom_passphrase_time() const;
 
+  // Restore a saved nigori obtained from OnLocalSetCustomPassphrase.
+  //
+  // Writes the nigori to the Directory and updates the Cryptographer.
+  void RestoreNigori(const SyncEncryptionHandler::NigoriState& nigori_state);
+
  private:
   friend class SyncEncryptionHandlerImplTest;
   FRIEND_TEST_ALL_PREFIXES(SyncEncryptionHandlerImplTest,
@@ -139,7 +144,10 @@ class SYNC_EXPORT_PRIVATE SyncEncryptionHandlerImpl
   // Iterate over all encrypted types ensuring each entry is properly encrypted.
   void ReEncryptEverything(WriteTransaction* trans);
 
-  // Apply a nigori update. Updates internal and cryptographer state.
+  // Updates internal and cryptographer state.
+  //
+  // Assumes |nigori| is already present in the Sync Directory.
+  //
   // Returns true on success, false if |nigori| was incompatible, and the
   // nigori node must be corrected.
   // Note: must be called from within a transaction.
@@ -261,6 +269,9 @@ class SYNC_EXPORT_PRIVATE SyncEncryptionHandlerImpl
   // (if known). Else return base::Time().
   base::Time GetExplicitPassphraseTime() const;
 
+  // Notify observers when a custom passphrase is set by this device.
+  void NotifyObserversOfLocalCustomPassphrase(WriteTransaction* trans);
+
   base::ThreadChecker thread_checker_;
 
   base::ObserverList<SyncEncryptionHandler::Observer> observers_;