Allow controlling the Instant field trial through a command line flag.

chrome/browser/instant/instant_field_trial.cc

 // 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.
 
 #include "chrome/browser/instant/instant_field_trial.h"
 
+#include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "chrome/browser/metrics/metrics_service.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/profiles/profile.h"
+#include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
 
 namespace {
 
 // Field trial IDs of the control and experiment groups. Though they are not
 // literally "const", they are set only once, in Activate() below.
 int g_control_group_id_1 = 0;
 int g_control_group_id_2 = 0;
 int g_experiment_group_id_1 = 0;
 int g_experiment_group_id_2 = 0;
@@ skipping 11 matching lines @@
   trial->UseOneTimeRandomization();
 
   g_control_group_id_1 = trial->AppendGroup("InstantControl1", 450);  // 45%
   g_control_group_id_2 = trial->AppendGroup("InstantControl2", 450);  // 45%
   g_experiment_group_id_1 = trial->AppendGroup("InstantExperiment1", 50);  // 5%
   g_experiment_group_id_2 = trial->AppendGroup("InstantExperiment2", 50);  // 5%
 }
 
 // static
 InstantFieldTrial::Group InstantFieldTrial::GetGroup(Profile* profile) {
+  CommandLine* command_line = CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kInstantFieldTrial)) {
+    std::string switch_value =
+        command_line->GetSwitchValueASCII(switches::kInstantFieldTrial);
+    if (switch_value == switches::kInstantFieldTrialInstant)
+      return EXPERIMENT1;
+    else
+      return INACTIVE;
+  }
+
   if (!profile || profile->IsOffTheRecord())
     return INACTIVE;
 
   const PrefService* prefs = profile->GetPrefs();
   if (!prefs ||
       !MetricsServiceHelper::IsMetricsReportingEnabled() ||
       !prefs->GetBoolean(prefs::kSearchSuggestEnabled) ||
       prefs->GetBoolean(prefs::kInstantEnabledOnce) ||
       prefs->IsManagedPreference(prefs::kInstantEnabled)) {
     return INACTIVE;
@@ skipping 37 matching lines @@
   switch (GetGroup(profile)) {
     case INACTIVE:    return std::string();
     case CONTROL1:    return "ix=c1&";
     case CONTROL2:    return "ix=c2&";
     case EXPERIMENT1: return "ix=e1&";
     case EXPERIMENT2: return "ix=e2&";
   }
   NOTREACHED();
   return std::string();
 }