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

net/base/host_resolver_impl.cc

Index: net/base/host_resolver_impl.cc
diff --git a/net/base/host_resolver_impl.cc b/net/base/host_resolver_impl.cc
index 894443cf76345989c7d895ba6e0a9a08fedbeefc..8b8984eea541f3ec4d0c4634ef4e3932f41a6dc4 100644
--- a/net/base/host_resolver_impl.cc
+++ b/net/base/host_resolver_impl.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.
 
@@ -566,9 +566,8 @@ class HostResolverImpl::Job
 
     UMA_HISTOGRAM_ENUMERATION("DNS.ResolveCategory", category, RESOLVE_MAX);
 
-    static bool show_speculative_experiment_histograms =
-        base::FieldTrialList::Find("DnsImpact") &&
-        !base::FieldTrialList::Find("DnsImpact")->group_name().empty();
+    static const bool show_speculative_experiment_histograms =
+        base::FieldTrialList::TrialExists("DnsImpact");
     if (show_speculative_experiment_histograms) {
       UMA_HISTOGRAM_ENUMERATION(
           base::FieldTrial::MakeName("DNS.ResolveCategory", "DnsImpact"),
@@ -578,9 +577,8 @@ class HostResolverImpl::Job
                                                  "DnsImpact"), duration);
       }
     }
-    static bool show_parallelism_experiment_histograms =
-        base::FieldTrialList::Find("DnsParallelism") &&
-        !base::FieldTrialList::Find("DnsParallelism")->group_name().empty();
+    static const bool show_parallelism_experiment_histograms =
+        base::FieldTrialList::TrialExists("DnsParallelism");
     if (show_parallelism_experiment_histograms) {
       UMA_HISTOGRAM_ENUMERATION(
           base::FieldTrial::MakeName("DNS.ResolveCategory", "DnsParallelism"),