Supporting command line argument to force field trials

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index e13c48ce280bd204cb67383da94f8901e579cdbe..335f6aeab65da03a5068fe2c5b768c2cc2ad4cb1 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -617,6 +617,20 @@ void ChromeBrowserMainParts::SetupMetricsAndFieldTrials() {
     metrics->ForceClientIdCreation();  // Needed below.
   field_trial_list_.reset(new base::FieldTrialList(metrics->GetClientId()));
 
+  // Ensure any field trials specified on the command line are initialized
+  // and stop the metrics service so that we don't pollute UMA.
+#ifndef NDEBUG
+  const CommandLine* command_line = CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kForceFieldTestNameAndValue)) {
+    std::string persistent = command_line->GetSwitchValueASCII(
+        switches::kForceFieldTestNameAndValue);
+    bool ret = base::FieldTrialList::CreateTrialsFromString(persistent);
+    CHECK(ret) << "Invalid --" << switches::kForceFieldTestNameAndValue <<
+                  " list specified.";
+    metrics->Stop();
+  }
+#endif  // NDEBUG
+
   SetupFieldTrials(metrics->recording_active(),
                    local_state_->IsManagedPreference(
                        prefs::kMaxConnectionsPerProxy));
@@ -640,7 +654,7 @@ void ChromeBrowserMainParts::ConnectionFieldTrial() {
 
   // After June 30, 2011 builds, it will always be in default group.
   scoped_refptr<base::FieldTrial> connect_trial(
-      new base::FieldTrial(
+      base::FieldTrial::CreateInstance(
           "ConnCountImpact", kConnectDivisor, "conn_count_6", 2011, 6, 30));
 
   // This (6) is the current default value. Having this group declared here
@@ -693,8 +707,9 @@ void ChromeBrowserMainParts::SocketTimeoutFieldTrial() {
 
   // After June 30, 2011 builds, it will always be in default group.
   scoped_refptr<base::FieldTrial> socket_timeout_trial(
-      new base::FieldTrial("IdleSktToImpact", kIdleSocketTimeoutDivisor,
-          "idle_timeout_10", 2011, 6, 30));
+      base::FieldTrial::CreateInstance(
+          "IdleSktToImpact", kIdleSocketTimeoutDivisor, "idle_timeout_10",
+          2011, 6, 30));
   const int socket_timeout_10 = socket_timeout_trial->kDefaultGroupNumber;
 
   const int socket_timeout_5 =
@@ -727,7 +742,8 @@ void ChromeBrowserMainParts::ProxyConnectionsFieldTrial() {
 
   // After June 30, 2011 builds, it will always be in default group.
   scoped_refptr<base::FieldTrial> proxy_connection_trial(
-      new base::FieldTrial("ProxyConnectionImpact", kProxyConnectionsDivisor,
+      base::FieldTrial::CreateInstance(
+          "ProxyConnectionImpact", kProxyConnectionsDivisor,
           "proxy_connections_32", 2011, 6, 30));
 
   // This (32 connections per proxy server) is the current default value.
@@ -781,9 +797,8 @@ void ChromeBrowserMainParts::SpdyFieldTrial() {
     base::FieldTrial::Probability npnhttp_probability = 5;
 
     // After June 30, 2013 builds, it will always be in default group.
-    scoped_refptr<base::FieldTrial> trial(
-        new base::FieldTrial(
-            "SpdyImpact", kSpdyDivisor, "npn_with_spdy", 2013, 6, 30));
+    scoped_refptr<base::FieldTrial> trial(base::FieldTrial::CreateInstance(
+        "SpdyImpact", kSpdyDivisor, "npn_with_spdy", 2013, 6, 30));
 
     // npn with spdy support is the default.
     int npn_spdy_grp = trial->kDefaultGroupNumber;
@@ -816,9 +831,8 @@ void ChromeBrowserMainParts::SpdyFieldTrial() {
 
   // After June 30, 2013 builds, it will always be in default group
   // (cwndDynamic).
-  scoped_refptr<base::FieldTrial> trial(
-      new base::FieldTrial(
-          "SpdyCwnd", kSpdyCwndDivisor, "cwndDynamic", 2013, 6, 30));
+  scoped_refptr<base::FieldTrial> trial(base::FieldTrial::CreateInstance(
+      "SpdyCwnd", kSpdyCwndDivisor, "cwndDynamic", 2013, 6, 30));
 
   trial->AppendGroup("cwnd10", kSpdyCwnd10);
   trial->AppendGroup("cwnd16", kSpdyCwnd16);
@@ -856,7 +870,7 @@ void ChromeBrowserMainParts::WarmConnectionFieldTrial() {
 
   // After January 30, 2013 builds, it will always be in default group.
   scoped_refptr<base::FieldTrial> warmest_socket_trial(
-      new base::FieldTrial(
+      base::FieldTrial::CreateInstance(
           "WarmSocketImpact", kWarmSocketDivisor, "last_accessed_socket",
           2013, 1, 30));
 
@@ -892,7 +906,7 @@ void ChromeBrowserMainParts::ConnectBackupJobsFieldTrial() {
     const base::FieldTrial::Probability kConnectBackupJobsProbability = 1;
     // After June 30, 2011 builds, it will always be in default group.
     scoped_refptr<base::FieldTrial> trial(
-        new base::FieldTrial("ConnnectBackupJobs",
+        base::FieldTrial::CreateInstance("ConnnectBackupJobs",
             kConnectBackupJobsDivisor, "ConnectBackupJobsEnabled", 2011, 6,
                 30));
     const int connect_backup_jobs_enabled = trial->kDefaultGroupNumber;
@@ -912,9 +926,8 @@ void ChromeBrowserMainParts::PredictorFieldTrial() {
 
   // After June 30, 2011 builds, it will always be in default group
   // (default_enabled_prefetch).
-  scoped_refptr<base::FieldTrial> trial(
-      new base::FieldTrial("DnsImpact", kDivisor,
-                           "default_enabled_prefetch", 2011, 10, 30));
+  scoped_refptr<base::FieldTrial> trial(base::FieldTrial::CreateInstance(
+      "DnsImpact", kDivisor, "default_enabled_prefetch", 2011, 10, 30));
 
   // First option is to disable prefetching completely.
   int disabled_prefetch = trial->AppendGroup("disabled_prefetch",
@@ -1021,7 +1034,7 @@ void ChromeBrowserMainParts::ComodoDNSExperimentFieldTrial() {
 
   // After April 15, 2012 builds, it will always be in default group.
   scoped_refptr<base::FieldTrial> trial(
-      new base::FieldTrial("ComodoDNSExperiment", kDivisor,
+      base::FieldTrial::CreateInstance("ComodoDNSExperiment", kDivisor,
           "inactive", 2012, 4, 15));
 
   const int active = trial->AppendGroup("active", kProbability);
@@ -1682,9 +1695,8 @@ int ChromeBrowserMainParts::PreMainMessageLoopRunImpl() {
     base::FieldTrial::Probability kSDCH_DIVISOR = 1000;
     base::FieldTrial::Probability kSDCH_DISABLE_PROBABILITY = 1;  // 0.1% prob.
     // After March 31, 2012 builds, it will always be in default group.
-    scoped_refptr<base::FieldTrial> sdch_trial(
-        new base::FieldTrial("GlobalSdch", kSDCH_DIVISOR, "global_enable_sdch",
-            2012, 3, 31));
+    scoped_refptr<base::FieldTrial> sdch_trial(base::FieldTrial::CreateInstance(
+        "GlobalSdch", kSDCH_DIVISOR, "global_enable_sdch", 2012, 3, 31));
     int sdch_enabled_group = sdch_trial->kDefaultGroupNumber;
 
     sdch_trial->AppendGroup("global_disable_sdch",