Introduce a field trial for Instant.

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/metrics/field_trial.h"
+#include "chrome/browser/prefs/pref_service.h"
+#include "chrome/browser/profiles/profile.h"
+#include "chrome/common/pref_names.h"
+
+namespace {
+
+const char kTrialId[] = "Instant";
+
+int kControl1 = 0;
+int kControl2 = 0;
+int kExperiment1 = 0;
+int kExperiment2 = 0;
+
+// Returns true if the user is in one of the given groups in the field trial.
+bool IsGroup(Profile* profile, const int group1, const int group2) {
+  if (profile->IsOffTheRecord())
+    return false;
+
+  const PrefService* prefs = profile->GetPrefs();
+  if (prefs &&
+      (prefs->GetBoolean(prefs::kInstantEnabledOnce) ||
+       prefs->IsManagedPreference(prefs::kInstantEnabled))) {
+    return false;
+  }
+
+  const int group = base::FieldTrialList::FindValue(kTrialId);
+  return group != base::FieldTrial::kNotFinalized &&
+         group != base::FieldTrial::kDefaultGroupNumber &&
+         (group == group1 || group == group2);
+}
+
+}  // namespace
+
+namespace instant_field_trial {
+
+void Init() {
+  scoped_refptr<base::FieldTrial> trial(
+      new base::FieldTrial(kTrialId, 1000, "InstantDefault", 2011, 9, 30));
+  if (!base::FieldTrialList::IsOneTimeRandomizationEnabled())
+    return;
+
+  trial->UseOneTimeRandomization();
+
+  kControl1 = trial->AppendGroup("InstantControl1", 250);
+  kControl2 = trial->AppendGroup("InstantControl2", 250);
+  kExperiment1 = trial->AppendGroup("InstantExperiment1", 250);
+  kExperiment2 = trial->AppendGroup("InstantExperiment2", 250);
+}
+
+bool IsExperiment(Profile* profile) {
+  return IsGroup(profile, kExperiment1, kExperiment2);
+}
+
+bool IsControl(Profile* profile) {
+  return IsGroup(profile, kControl1, kControl2);
+}
+
+std::string GetGroupName(Profile* profile) {
+  if (profile->IsOffTheRecord())
+    return "InstantIncognito";
+
+  const PrefService* prefs = profile->GetPrefs();
+  if (prefs &&
+      (prefs->GetBoolean(prefs::kInstantEnabledOnce) ||
+       prefs->IsManagedPreference(prefs::kInstantEnabled))) {
+    return prefs->GetBoolean(prefs::kInstantEnabled) ? "InstantEnabled"
+                                                     : "InstantDisabled";
+  }
+
+  return base::FieldTrialList::FindFullName(kTrialId);
+}
+
+}  // namespace instant_field_trial