[Sync] Add keystore encryption info to about:sync

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 f54055b9afdaab82647e0088a353b499de792524..33c06e52c4969ff8171a9d7109eebc4030ca7cb6 100644
--- a/sync/internal_api/sync_encryption_handler_impl.h
+++ b/sync/internal_api/sync_encryption_handler_impl.h
@@ -62,9 +62,6 @@ class SyncEncryptionHandlerImpl
   virtual bool EncryptEverythingEnabled() const OVERRIDE;
   virtual PassphraseType GetPassphraseType() const OVERRIDE;
 
-  // TODO(zea): provide a method for getting the time at which the nigori
-  // node was migrated.
-
   // NigoriHandler implementation.
   // Note: all methods are invoked while the caller holds a transaction.
   virtual void ApplyNigoriUpdate(
@@ -88,6 +85,7 @@ class SyncEncryptionHandlerImpl
   ModelTypeSet GetEncryptedTypesUnsafe();
 
   bool MigratedToKeystore();
+  base::Time GetKeystoreMigrationTime() const;
 
  private:
   FRIEND_TEST_ALL_PREFIXES(SyncEncryptionHandlerImplTest,