Remove the remnants of the WarmSocketImpact field trial.

net/url_request/url_request_http_job.cc

Index: net/url_request/url_request_http_job.cc
diff --git a/net/url_request/url_request_http_job.cc b/net/url_request/url_request_http_job.cc
index 988ecdbcf808c0656442f954775a08956adcd945..b518b95259f6ce3bb8506cbd47a13edd140db072 100644
--- a/net/url_request/url_request_http_job.cc
+++ b/net/url_request/url_request_http_job.cc
@@ -1289,15 +1289,6 @@ void URLRequestHttpJob::RecordTimer() {
         to_start);
   }
 
-  static const bool use_warm_socket_impact_histogram =
-      base::FieldTrialList::TrialExists("WarmSocketImpact");
-  if (use_warm_socket_impact_histogram) {
-    UMA_HISTOGRAM_MEDIUM_TIMES(
-        base::FieldTrial::MakeName("Net.HttpTimeToFirstByte",
-                                   "WarmSocketImpact"),
-        to_start);
-  }
-
   static const bool use_prefetch_histogram =
       base::FieldTrialList::TrialExists("Prefetch");
   if (use_prefetch_histogram) {