Do not fetch a new config if one is already in progress.

components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client.h

Index: components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client.h
diff --git a/components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client.h b/components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client.h
index e9b1332ca59e6eb7f6edc1ce8ba2e131661a25de..c14d723f453f5e313c412bdc8990f6dc281cf65a 100644
--- a/components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client.h
+++ b/components/data_reduction_proxy/core/browser/data_reduction_proxy_config_service_client.h
@@ -276,6 +276,9 @@ class DataReductionProxyConfigServiceClient
   // Time when the IP address last changed.
   base::TimeTicks last_ip_address_change_;
 
+  // True if a client config fetch is in progress.
+  bool fetch_in_progress_;
+
   // Enforce usage on the IO thread.
   base::ThreadChecker thread_checker_;