Hard coded finch config for Popular site

components/ntp_tiles/field_trial.cc

+// Copyright 2016 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 "base/metrics/field_trial.h"
+
+#if defined(OS_ANDROID)
+#include <jni.h>
+#endif
+
+#include "base/command_line.h"
+#include "base/metrics/field_trial.h"
+#include "base/strings/string_util.h"
+#include "components/ntp_tiles/constants.h"
+#include "components/ntp_tiles/field_trial.h"
+#include "components/ntp_tiles/switches.h"
+
+#if defined(OS_ANDROID)
+#include "base/android/jni_android.h"
+#include "jni/MostVisitedSites_jni.h"
+#endif
+
+const char kPopularSiteDefaultGroup[] = "Default";

[Alexei Svitkine (slow), 2016/11/16 00:52:53]

Nit: Put in anon namespace.

[noyau (Ping after 24h), 2016/11/16 12:28:02]

Done.

+const char kPopularSiteControlGroup[] = "Control";
+const char kPopularSiteEnabledGroup[] = "Enabled";
+const char kPopularSiteEnabledCommandLineSwitchGroup[] =
+    "EnabledWithCommandLineSwitch";
+const char kPopularSiteDisabledCommandLineSwitchGroup[] =
+    "DisabledWithCommandLineSwitch";
+
+// On iOS it is not technically possible to prep the field trials on first
+// launch, the configuration file is downloaded too late. In order to run some
+// experiments that need to be active on first launch to be meaningful these
+// are hardcoded, but can be superceeded by a server side config on subsequent
+// launches.
+void ntp_tiles::SetUpFirstLaunchFieldTrial(bool is_stable_channel) {

[Alexei Svitkine (slow), 2016/11/16 00:52:53]

Nit: Specifying namespace like this is not usually done in Chrome code - suggest
explicitly surrounding in a namespace block instead.

[noyau (Ping after 24h), 2016/11/16 12:28:02]

Done.

+  // Check first if a server side config superceeded this experiment.
+  if (base::FieldTrialList::TrialExists(kPopularSitesFieldTrialName))
+    return;
+
+  // Stable channels will run with 10% probability.
+  // Non-stable channels will run with 50% probability.
+  const base::FieldTrial::Probability kTotalProbability = 100;
+  const base::FieldTrial::Probability kEnabledAndControlProbability =
+      is_stable_channel ? 10 : 50;
+
+  // Experiment enabled until March 15, 2017. By default, disabled.
+  scoped_refptr<base::FieldTrial> trial(
+      base::FieldTrialList::FactoryGetFieldTrial(
+          kPopularSitesFieldTrialName, kTotalProbability,
+          kPopularSiteDefaultGroup, 2017, 3, 15,  // Mar 15, 2017
+          base::FieldTrial::ONE_TIME_RANDOMIZED, NULL));

[Alexei Svitkine (slow), 2016/11/16 00:52:53]

nullptr

[noyau (Ping after 24h), 2016/11/16 12:28:02]

Done.

+
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(ntp_tiles::switches::kEnableNTPPopularSites)) {
+    trial->AppendGroup(kPopularSiteEnabledCommandLineSwitchGroup,
+                       kTotalProbability);
+  } else if (command_line->HasSwitch(
+                 ntp_tiles::switches::kDisableNTPPopularSites)) {
+    trial->AppendGroup(kPopularSiteDisabledCommandLineSwitchGroup,
+                       kTotalProbability);
+  } else {
+    trial->AppendGroup(kPopularSiteControlGroup, kEnabledAndControlProbability);
+    trial->AppendGroup(kPopularSiteEnabledGroup, kEnabledAndControlProbability);
+  }
+  trial->group();

[Alexei Svitkine (slow), 2016/11/16 00:52:53]

Suggest leaving this out.

This way, the trial will only be marked active when the group is queried by code
that actually cares about the trial state. This should also make it consistent
with the TrialExists case.

[noyau (Ping after 24h), 2016/11/16 12:28:02]

Done.

+}
+
+bool ntp_tiles::ShouldShowPopularSites() {
+  // Note: It's important to query the field trial state first, to ensure that
+  // UMA reports the correct group.
+  const std::string group_name =
+      base::FieldTrialList::FindFullName(kPopularSitesFieldTrialName);
+
+  base::CommandLine* cmd_line = base::CommandLine::ForCurrentProcess();
+  if (cmd_line->HasSwitch(switches::kDisableNTPPopularSites))
+    return false;
+
+  if (cmd_line->HasSwitch(switches::kEnableNTPPopularSites))
+    return true;
+
+#if defined(OS_ANDROID)
+  if (Java_MostVisitedSites_isPopularSitesForceEnabled(
+          base::android::AttachCurrentThread())) {
+    return true;
+  }
+#endif
+
+  return base::StartsWith(group_name, "Enabled",
+                          base::CompareCase::INSENSITIVE_ASCII);
+}