Replace ToLower calls to the new format

chromeos/login/auth/key.cc

Index: chromeos/login/auth/key.cc
diff --git a/chromeos/login/auth/key.cc b/chromeos/login/auth/key.cc
index 01c3bcf1ffc89a03b21dc468d4b66b1374a4e01c..fe3ec86a74072a6b32c51c2aa736d67250e235fb 100644
--- a/chromeos/login/auth/key.cc
+++ b/chromeos/login/auth/key.cc
@@ -84,7 +84,7 @@ void Key::Transform(KeyType target_key_type, const std::string& salt) {
       // Keep only the first half of the hash for 'weak' hashing so that the
       // plain text secret cannot be reconstructed even if the hashing is
       // reversed.
-      secret_ = base::StringToLowerASCII(base::HexEncode(
+      secret_ = base::ToLowerASCII(base::HexEncode(
           reinterpret_cast<const void*>(hash), sizeof(hash) / 2));
       break;
     }