clang/win: Let remaining chromium_code targets build with -Wextra.

rlz/win/lib/rlz_value_store_registry.cc

Index: rlz/win/lib/rlz_value_store_registry.cc
diff --git a/rlz/win/lib/rlz_value_store_registry.cc b/rlz/win/lib/rlz_value_store_registry.cc
index 4a133ebc7d4e2e5e6285d09e75e424a82360a553..b88707babbd7d3c86b76e9ae255791477df7e085 100644
--- a/rlz/win/lib/rlz_value_store_registry.cc
+++ b/rlz/win/lib/rlz_value_store_registry.cc
@@ -349,7 +349,7 @@ void RlzValueStoreRegistry::CollectGarbage() {
     kPingTimesSubkeyName
   };
 
-  for (int i = 0; i < arraysize(subkeys); i++) {
+  for (size_t i = 0; i < arraysize(subkeys); i++) {
     std::string subkey_name;
     base::StringAppendF(&subkey_name, "%s\\%s", kLibKeyName, subkeys[i]);
     AppendBrandToString(&subkey_name);