Add one-time randomization support for FieldTrial, and the ability to

net/socket/client_socket_pool_histograms.cc

Index: net/socket/client_socket_pool_histograms.cc
diff --git a/net/socket/client_socket_pool_histograms.cc b/net/socket/client_socket_pool_histograms.cc
index 202112bf567e6f3ae4f5fa68ec9e4c9c4dfef155..5c3bddb14af893963d31e55ee09451680b4a076f 100644
--- a/net/socket/client_socket_pool_histograms.cc
+++ b/net/socket/client_socket_pool_histograms.cc
@@ -1,4 +1,4 @@
-// Copyright (c) 2010 The Chromium Authors. All rights reserved.
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
@@ -58,10 +58,8 @@ void ClientSocketPoolHistograms::AddSocketType(int type) const {
 void ClientSocketPoolHistograms::AddRequestTime(base::TimeDelta time) const {
   request_time_->AddTime(time);
 
-  static bool proxy_connection_impact_trial_exists(
-      base::FieldTrialList::Find("ProxyConnectionImpact") &&
-      !base::FieldTrialList::Find("ProxyConnectionImpact")->
-          group_name().empty());
+  static const bool proxy_connection_impact_trial_exists =
+      base::FieldTrialList::TrialExists("ProxyConnectionImpact");
   if (proxy_connection_impact_trial_exists && is_http_proxy_connection_) {
     UMA_HISTOGRAM_CUSTOM_TIMES(
         base::FieldTrial::MakeName("Net.HttpProxySocketRequestTime",