Restoring the chrome variatioons client, with a fix for browser_test failures caused by it.

chrome/browser/metrics/variations_service.cc

Index: chrome/browser/metrics/variations_service.cc
diff --git a/chrome/browser/metrics/variations_service.cc b/chrome/browser/metrics/variations_service.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8b9866fd727a562d568a0cbb3c961a48a54bad10
--- /dev/null
+++ b/chrome/browser/metrics/variations_service.cc
@@ -0,0 +1,279 @@
+// Copyright (c) 2012 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/metrics/variations_service.h"
+
+#include "base/base64.h"
+#include "base/build_time.h"
+#include "base/version.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/metrics/field_trial.h"
+#include "chrome/browser/browser_process.h"
+#include "chrome/browser/metrics/proto/trials_seed.pb.h"
+#include "chrome/browser/prefs/pref_service.h"
+#include "chrome/common/pref_names.h"
+#include "content/public/common/url_fetcher.h"
+#include "googleurl/src/gurl.h"
+#include "net/base/load_flags.h"
+#include "net/base/network_change_notifier.h"
+#include "net/url_request/url_request_status.h"
+
+namespace {
+
+// Default server of Variations seed info.
+const char kDefaultVariationsServer[] =
+    "https://clients4.google.com/chrome-variations/seed";
+const int kMaxRetrySeedFetch = 5;
+
+// Maps chrome_variations::Study_Channel enum values to corresponding
+// chrome::VersionInfo::Channel enum values.
+chrome::VersionInfo::Channel ConvertStudyChannelToVersionChannel(
+    chrome_variations::Study_Channel study_channel) {
+  switch (study_channel) {
+    case chrome_variations::Study_Channel_CANARY:
+      return chrome::VersionInfo::CHANNEL_CANARY;
+    case chrome_variations::Study_Channel_DEV:
+      return chrome::VersionInfo::CHANNEL_DEV;
+    case chrome_variations::Study_Channel_BETA:
+      return chrome::VersionInfo::CHANNEL_BETA;
+    case chrome_variations::Study_Channel_STABLE:
+      return chrome::VersionInfo::CHANNEL_STABLE;
+  }
+  // All enum values of |study_channel| were handled above.
+  NOTREACHED();
+  return chrome::VersionInfo::CHANNEL_UNKNOWN;
+}
+
+}  // namespace
+
+VariationsService::VariationsService() {}
+VariationsService::~VariationsService() {}
+
+bool VariationsService::CreateTrialsFromSeed(PrefService* local_prefs) {
+  chrome_variations::TrialsSeed seed;
+  if (!LoadTrialsSeedFromPref(local_prefs, &seed))
+      return false;
+
+  for (int i = 0; i < seed.study_size(); ++i)
+    CreateTrialFromStudy(seed.study(i));
+
+  return true;
+}
+
+void VariationsService::StartFetchingVariationsSeed() {
+  if (net::NetworkChangeNotifier::IsOffline())
+    return;
+
+  pending_seed_request_.reset(content::URLFetcher::Create(
+      GURL(kDefaultVariationsServer), net::URLFetcher::GET, this));
+  pending_seed_request_->SetLoadFlags(net::LOAD_DO_NOT_SEND_COOKIES |
+                                      net::LOAD_DO_NOT_SAVE_COOKIES);
+  pending_seed_request_->SetRequestContext(
+      g_browser_process->system_request_context());
+  pending_seed_request_->SetMaxRetries(kMaxRetrySeedFetch);
+  pending_seed_request_->Start();
+}
+
+void VariationsService::OnURLFetchComplete(const net::URLFetcher* source) {
+  DCHECK_EQ(pending_seed_request_.get(), source);
+  // When we're done handling the request, the fetcher will be deleted.
+  scoped_ptr<const content::URLFetcher> request(
+      pending_seed_request_.release());
+  if (request->GetStatus().status() != net::URLRequestStatus::SUCCESS ||
+      request->GetResponseCode() != 200)
+    return;
+
+  std::string seed_data;
+  request->GetResponseAsString(&seed_data);
+
+  StoreSeedData(seed_data, g_browser_process->local_state());
+}
+
+// static
+void VariationsService::RegisterPrefs(PrefService* prefs) {
+  prefs->RegisterStringPref(prefs::kVariationsSeed, std::string());
+}
+
+void VariationsService::StoreSeedData(const std::string& seed_data,
+                                      PrefService* local_prefs) {
+  // Only store the seed data if it parses correctly.
+  chrome_variations::TrialsSeed seed;
+  if (!seed.ParseFromString(seed_data)) {
+    VLOG(1) << "Variations Seed data from server is not in valid proto format, "
+            << "rejecting the seed.";
+    return;
+  }
+  std::string base64_seed_data;
+  if (!base::Base64Encode(seed_data, &base64_seed_data)) {
+    VLOG(1) << "Variations Seed data from server fails Base64Encode, rejecting "
+            << "the seed.";
+    return;
+  }
+  local_prefs->SetString(prefs::kVariationsSeed, base64_seed_data);
+}
+
+// static
+bool VariationsService::ShouldAddStudy(const chrome_variations::Study& study) {
+  const chrome::VersionInfo current_version_info;
+  if (!current_version_info.is_valid())
+    return false;
+
+  if (!CheckStudyChannel(study, chrome::VersionInfo::GetChannel())) {
+    DVLOG(1) << "Filtered out study " << study.name() << " due to version.";
+    return false;
+  }
+
+  if (!CheckStudyVersion(study, current_version_info.Version())) {
+    DVLOG(1) << "Filtered out study " << study.name() << " due to version.";
+    return false;
+  }
+
+  // Use build time and not system time to match what is done in field_trial.cc.
+  if (!CheckStudyDate(study, base::GetBuildTime())) {
+    DVLOG(1) << "Filtered out study " << study.name() << " due to date.";
+    return false;
+  }
+
+  DVLOG(1) << "Kept study " << study.name() << ".";
+  return true;
+}
+
+// static
+bool VariationsService::CheckStudyChannel(
+    const chrome_variations::Study& study,
+    chrome::VersionInfo::Channel channel) {
+  if (study.channel_size() == 0) {
+    // An empty channel list matches all channels.
+    return true;
+  }
+
+  for (int i = 0; i < study.channel_size(); ++i) {
+    if (ConvertStudyChannelToVersionChannel(study.channel(i)) == channel)
+      return true;
+  }
+  return false;
+}
+
+// static
+bool VariationsService::CheckStudyVersion(const chrome_variations::Study& study,
+                                          const std::string& version_string) {
+  const Version current_version(version_string);
+  if (!current_version.IsValid()) {
+    DCHECK(false);
+    return false;
+  }
+
+  if (study.has_min_version()) {
+    const Version min_version(study.min_version());
+    if (!min_version.IsValid())
+      return false;
+    if (current_version.CompareTo(min_version) < 0)
+      return false;
+  }
+
+  if (study.has_max_version()) {
+    const Version max_version(study.max_version());
+    if (!max_version.IsValid())
+      return false;
+    if (current_version.CompareTo(max_version) > 0)
+      return false;
+  }
+
+  return true;
+}
+
+// static
+bool VariationsService::CheckStudyDate(const chrome_variations::Study& study,
+                                       const base::Time& date_time) {
+  const base::Time epoch = base::Time::UnixEpoch();
+
+  if (study.has_start_date()) {
+    const base::Time start_date =
+        epoch + base::TimeDelta::FromSeconds(study.start_date());
+    if (date_time < start_date)
+      return false;
+  }
+
+  if (study.has_expiry_date()) {
+    const base::Time expiry_date =
+        epoch + base::TimeDelta::FromSeconds(study.expiry_date());
+    if (date_time >= expiry_date)
+      return false;
+  }
+
+  return true;
+}
+
+bool VariationsService::LoadTrialsSeedFromPref(
+    PrefService* local_prefs,
+    chrome_variations::TrialsSeed* seed) {
+  std::string base64_seed_data = local_prefs->GetString(prefs::kVariationsSeed);
+  std::string seed_data;
+
+  // If the decode process fails, assume the pref value is corrupt, and clear
+  // it.
+  if (!base::Base64Decode(base64_seed_data, &seed_data) ||
+      !seed->ParseFromString(seed_data)) {
+    VLOG(1) << "Variations Seed data in local pref is corrupt, clearing the "
+            << "pref.";
+    local_prefs->ClearPref(prefs::kVariationsSeed);
+    return false;
+  }
+  return true;
+}
+
+void VariationsService::CreateTrialFromStudy(
+    const chrome_variations::Study& study) {
+  if (!ShouldAddStudy(study))
+    return;
+
+  // At the moment, a missing default_experiment_name makes the study invalid.
+  if (!study.has_default_experiment_name()) {
+    DVLOG(1) << study.name() << " has no default experiment defined.";
+    return;
+  }
+
+  const std::string& default_group_name = study.default_experiment_name();
+  base::FieldTrial::Probability divisor = 0;
+
+  bool found_default_group = false;
+  for (int i = 0; i < study.experiment_size(); ++i) {
+    divisor += study.experiment(i).probability_weight();
+    if (study.experiment(i).name() == default_group_name)
+      found_default_group = true;
+  }
+  if (!found_default_group) {
+    DVLOG(1) << study.name() << " is missing default experiment in it's "
+             << "experiment list";
+    // The default group was not found in the list of groups. This study is not
+    // valid.
+    return;
+  }
+
+  const base::Time epoch = base::Time::UnixEpoch();
+  const base::Time expiry_date =
+      epoch + base::TimeDelta::FromSeconds(study.expiry_date());
+  base::Time::Exploded exploded_end_date;
+  expiry_date.UTCExplode(&exploded_end_date);
+
+  scoped_refptr<base::FieldTrial> trial(
+      base::FieldTrialList::FactoryGetFieldTrial(
+          study.name(), divisor, default_group_name, exploded_end_date.year,
+          exploded_end_date.month, exploded_end_date.day_of_month, NULL));
+
+  if (study.has_consistency() &&
+      study.consistency() == chrome_variations::Study_Consistency_PERMANENT) {
+    trial->UseOneTimeRandomization();
+  }
+
+  for (int i = 0; i < study.experiment_size(); ++i) {
+    if (study.experiment(i).name() != default_group_name) {
+      trial->AppendGroup(study.experiment(i).name(),
+                         study.experiment(i).probability_weight());
+    }
+  }
+
+  // TODO(jwd): Add experiment_id association code.
+  trial->SetForced();
+}