Reinstate one check, fix fall out
diff --git a/BUILD b/BUILD
index f6187e0..5f89638 100644
--- a/BUILD
+++ b/BUILD
@@ -511,7 +511,7 @@
         "src/core/lib/json/json_reader.c",
         "src/core/lib/json/json_string.c",
         "src/core/lib/json/json_writer.c",
-        "src/core/lib/security/util/b64.c",
+        "src/core/lib/slice/b64.c",
         "src/core/lib/slice/percent_encoding.c",
         "src/core/lib/slice/slice.c",
         "src/core/lib/slice/slice_buffer.c",
@@ -630,7 +630,7 @@
         "src/core/lib/json/json_common.h",
         "src/core/lib/json/json_reader.h",
         "src/core/lib/json/json_writer.h",
-        "src/core/lib/security/util/b64.h",
+        "src/core/lib/slice/b64.h",
         "src/core/lib/slice/percent_encoding.h",
         "src/core/lib/slice/slice_hash_table.h",
         "src/core/lib/slice/slice_internal.h",
@@ -911,7 +911,7 @@
         "src/core/lib/security/transport/security_handshaker.c",
         "src/core/lib/security/transport/server_auth_filter.c",
         "src/core/lib/security/transport/tsi_error.c",
-        "src/core/lib/security/util/b64.c",
+        "src/core/lib/slice/b64.c",
         "src/core/lib/security/util/json_util.c",
         "src/core/lib/surface/init_secure.c",
     ],
@@ -934,7 +934,7 @@
         "src/core/lib/security/transport/security_connector.h",
         "src/core/lib/security/transport/security_handshaker.h",
         "src/core/lib/security/transport/tsi_error.h",
-        "src/core/lib/security/util/b64.h",
+        "src/core/lib/slice/b64.h",
         "src/core/lib/security/util/json_util.h",
     ],
     language = "c",