Improve performance of proxy resolver by tracing DNS dependencies.

net/proxy/proxy_resolver_winhttp.cc

Index: net/proxy/proxy_resolver_winhttp.cc
diff --git a/net/proxy/proxy_resolver_winhttp.cc b/net/proxy/proxy_resolver_winhttp.cc
index 1e14fbb51bf1252c33c385c2a0e10d9e0104e75b..1ddc8ca4c2c58341f59d50b950b4247d411e9c04 100644
--- a/net/proxy/proxy_resolver_winhttp.cc
+++ b/net/proxy/proxy_resolver_winhttp.cc
@@ -128,11 +128,6 @@ LoadState ProxyResolverWinHttp::GetLoadState(RequestHandle request) const {
   return LOAD_STATE_IDLE;
 }
 
-LoadState ProxyResolverWinHttp::GetLoadStateThreadSafe(
-    RequestHandle request) const {
-  return LOAD_STATE_IDLE;
-}
-
 void ProxyResolverWinHttp::CancelSetPacScript() {
   NOTREACHED();
 }