Remove use of void** from HttpResponseHeaders::EnumerateHeaderLines

ios/web/public/test/response_providers/data_response_provider.mm

Index: ios/web/public/test/response_providers/data_response_provider.mm
diff --git a/ios/web/public/test/response_providers/data_response_provider.mm b/ios/web/public/test/response_providers/data_response_provider.mm
index a109dbee133bea2cc8c7197b8a9b05a1b89bdfcf..41e20acbc633bc15aa51cf238865572086886052 100644
--- a/ios/web/public/test/response_providers/data_response_provider.mm
+++ b/ios/web/public/test/response_providers/data_response_provider.mm
@@ -17,10 +17,10 @@ GCDWebServerResponse* DataResponseProvider::GetGCDWebServerResponse(
   GCDWebServerDataResponse* data_response = [GCDWebServerDataResponse
       responseWithHTML:base::SysUTF8ToNSString(response_body)];
   data_response.statusCode = response_headers->response_code();
-  void* iter = nullptr;
+  size_t iter = 0;
   std::string name;
   std::string value;
-  while (response_headers->EnumerateHeaderLines(&iter, &name, &value)) {
+  while (response_headers->EnumerateHeaderLines(iter, &name, &value)) {
     // TODO(crbug.com/435350): Extract out other names that can't be set by
     // using the |setValue:forAdditionalHeader:| API such as "ETag" etc.
     if (name == "Content-type") {