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

disable field trials. I am going to have a need for both soon.

Cleaning up some comments about empty trial names, adding static
method TrialExists() and simplifying many call sites by using this
method.

While I'm in there and needing base/OWNERS approval, add an OWNERS
file for base/metrics that adds jar@chromium.org as an owner for that
directory.

BUG=none
TEST=base_unittests
TBR=jam@chromium.org

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@84197 0039d316-1c4b-4281-b951-d872f2087c98

7 files changed, 17 insertions, 26 deletions

diff --git a/net/base/host_resolver_impl.cc b/net/base/host_resolver_impl.cc
index 8b33229..8c9d17f 100644
--- a/net/base/host_resolver_impl.cc
+++ b/net/base/host_resolver_impl.cc
@@ -554,9 +554,8 @@ 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"),
@@ -566,9 +565,8 @@ 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"),
diff --git a/net/http/http_cache_transaction.cc b/net/http/http_cache_transaction.cc
index 552913f..3b2b77c 100644
--- a/net/http/http_cache_transaction.cc
+++ b/net/http/http_cache_transaction.cc
@@ -865,8 +865,7 @@ int HttpCache::Transaction::DoAddToEntryComplete(int result) {
       base::TimeTicks::Now() - entry_lock_waiting_since_;
   UMA_HISTOGRAM_TIMES("HttpCache.EntryLockWait", entry_lock_wait);
   static const bool prefetching_fieldtrial =
-      base::FieldTrialList::Find("Prefetch") &&
-      !base::FieldTrialList::Find("Prefetch")->group_name().empty();
+      base::FieldTrialList::TrialExists("Prefetch");
   if (prefetching_fieldtrial) {
     UMA_HISTOGRAM_TIMES(
         base::FieldTrial::MakeName("HttpCache.EntryLockWait", "Prefetch"),
diff --git a/net/http/http_network_transaction.cc b/net/http/http_network_transaction.cc
index 46858e6..604d793 100644
--- a/net/http/http_network_transaction.cc
+++ b/net/http/http_network_transaction.cc
@@ -1007,9 +1007,8 @@ void HttpNetworkTransaction::LogTransactionConnectedMetrics() {
         base::TimeDelta::FromMilliseconds(1), base::TimeDelta::FromMinutes(10),
         100);
 
-  static bool use_conn_impact_histogram(
-      base::FieldTrialList::Find("ConnCountImpact") &&
-      !base::FieldTrialList::Find("ConnCountImpact")->group_name().empty());
+  static const bool use_conn_impact_histogram =
+      base::FieldTrialList::TrialExists("ConnCountImpact");
   if (use_conn_impact_histogram) {
     UMA_HISTOGRAM_CLIPPED_TIMES(
         base::FieldTrial::MakeName("Net.Transaction_Connected_New",
@@ -1020,8 +1019,8 @@ void HttpNetworkTransaction::LogTransactionConnectedMetrics() {
     }
   }
 
-  static bool use_spdy_histogram(base::FieldTrialList::Find("SpdyImpact") &&
-      !base::FieldTrialList::Find("SpdyImpact")->group_name().empty());
+  static const bool use_spdy_histogram =
+      base::FieldTrialList::TrialExists("SpdyImpact");
   if (use_spdy_histogram && response_.was_npn_negotiated) {
     UMA_HISTOGRAM_CLIPPED_TIMES(
       base::FieldTrial::MakeName("Net.Transaction_Connected_Under_10",
diff --git a/net/socket/client_socket_pool_histograms.cc b/net/socket/client_socket_pool_histograms.cc
index 202112b..5c3bddb 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",
diff --git a/net/socket/ssl_client_socket_pool.cc b/net/socket/ssl_client_socket_pool.cc
index 5f8daa7..7bde6d0 100644
--- a/net/socket/ssl_client_socket_pool.cc
+++ b/net/socket/ssl_client_socket_pool.cc
@@ -347,9 +347,8 @@ int SSLConnectJob::DoSSLConnectComplete(int result) {
                                    100);
       }
 
-      static bool false_start_trial(
-          base::FieldTrialList::Find("SSLFalseStart") &&
-          !base::FieldTrialList::Find("SSLFalseStart")->group_name().empty());
+      static const bool false_start_trial =
+          base::FieldTrialList::TrialExists("SSLFalseStart");
       if (false_start_trial) {
         UMA_HISTOGRAM_CUSTOM_TIMES(base::FieldTrial::MakeName(
                                        "Net.SSL_Connection_Latency",
diff --git a/net/socket/stream_socket.cc b/net/socket/stream_socket.cc
index 37482b4..3ef24c0 100644
--- a/net/socket/stream_socket.cc
+++ b/net/socket/stream_socket.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.
 
@@ -134,8 +134,7 @@ void StreamSocket::UseHistory::EmitPreconnectionHistograms() const {
   UMA_HISTOGRAM_ENUMERATION("Net.PreconnectUtilization2", result, 9);
 
   static const bool connect_backup_jobs_fieldtrial =
-      base::FieldTrialList::Find("ConnnectBackupJobs") &&
-      !base::FieldTrialList::Find("ConnnectBackupJobs")->group_name().empty();
+      base::FieldTrialList::TrialExists("ConnnectBackupJobs");
   if (connect_backup_jobs_fieldtrial) {
     UMA_HISTOGRAM_ENUMERATION(
         base::FieldTrial::MakeName("Net.PreconnectUtilization2",
diff --git a/net/url_request/url_request_http_job.cc b/net/url_request/url_request_http_job.cc
index cfb6ffc..ae87029 100644
--- a/net/url_request/url_request_http_job.cc
+++ b/net/url_request/url_request_http_job.cc
@@ -1123,8 +1123,7 @@ void URLRequestHttpJob::RecordTimer() {
   request_creation_time_ = base::Time();
 
   static const bool use_prefetch_histogram =
-      base::FieldTrialList::Find("Prefetch") &&
-      !base::FieldTrialList::Find("Prefetch")->group_name().empty();
+      base::FieldTrialList::TrialExists("Prefetch");
 
   UMA_HISTOGRAM_MEDIUM_TIMES("Net.HttpTimeToFirstByte", to_start);
   if (use_prefetch_histogram) {