Refactor MetricsStateManager class out of MetricsService.

chrome/browser/metrics/metrics_state_manager.cc

Index: chrome/browser/metrics/metrics_state_manager.cc
===================================================================
--- chrome/browser/metrics/metrics_state_manager.cc	(revision 0)
+++ chrome/browser/metrics/metrics_state_manager.cc	(working copy)
@@ -0,0 +1,233 @@
+// Copyright 2014 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/metrics_state_manager.h"
+
+#include "base/command_line.h"
+#include "base/guid.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
+#include "base/prefs/pref_registry_simple.h"
+#include "base/prefs/pref_service.h"
+#include "base/rand_util.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/time/time.h"
+#include "chrome/browser/metrics/cloned_install_detector.h"
+#include "chrome/browser/metrics/machine_id_provider.h"
+#include "chrome/common/chrome_switches.h"
+#include "chrome/common/metrics/caching_permuted_entropy_provider.h"
+#include "chrome/common/pref_names.h"
+
+#if defined(OS_CHROMEOS)
+#include "chrome/browser/chromeos/settings/cros_settings.h"
+#endif
+
+namespace metrics {
+
+namespace {
+
+// The argument used to generate a non-identifying entropy source. We want no
+// more than 13 bits of entropy, so use this max to return a number in the range
+// [0, 7999] as the entropy source (12.97 bits of entropy).
+const int kMaxLowEntropySize = 8000;
+
+// Default prefs value for prefs::kMetricsLowEntropySource to indicate that the
+// value has not yet been set.
+const int kLowEntropySourceNotSet = -1;
+
+// Generates a new non-identifying entropy source used to seed persistent
+// activities.
+int GenerateLowEntropySource() {
+  return base::RandInt(0, kMaxLowEntropySize - 1);
+}
+
+}  // namespace
+
+// static
+bool MetricsStateManager::instance_exists_ = false;
+
+MetricsStateManager::MetricsStateManager(PrefService* local_state)
+    : local_state_(local_state),
+      low_entropy_source_(kLowEntropySourceNotSet),
+      entropy_source_returned_(ENTROPY_SOURCE_NONE) {
+  ResetMetricsIDsIfNecessary();
+  if (IsMetricsReportingEnabled())
+    ForceClientIdCreation();
+
+  DCHECK(!instance_exists_);
+  instance_exists_ = true;
+}
+
+MetricsStateManager::~MetricsStateManager() {
+  DCHECK(instance_exists_);
+  instance_exists_ = false;
+}
+
+bool MetricsStateManager::IsMetricsReportingEnabled() {
+  // If the user permits metrics reporting with the checkbox in the
+  // prefs, we turn on recording.  We disable metrics completely for
+  // non-official builds.  This can be forced with a flag.
+  const CommandLine* command_line = CommandLine::ForCurrentProcess();
+  if (command_line->HasSwitch(switches::kEnableMetricsReportingForTesting))
+    return true;
+
+  // Disable metrics reporting when field trials are forced.
+  if (command_line->HasSwitch(switches::kForceFieldTrials))
+    return false;
+
+  bool enabled = false;
+#if defined(GOOGLE_CHROME_BUILD)
+#if defined(OS_CHROMEOS)
+  chromeos::CrosSettings::Get()->GetBoolean(chromeos::kStatsReportingPref,
+                                            &enabled);
+#else
+  enabled = local_state->GetBoolean(prefs::kMetricsReportingEnabled);
+#endif  // #if defined(OS_CHROMEOS)
+#endif  // defined(GOOGLE_CHROME_BUILD)
+  return enabled;
+}
+
+void MetricsStateManager::ForceClientIdCreation() {
+  if (!client_id_.empty())
+    return;
+
+  client_id_ = local_state_->GetString(prefs::kMetricsClientID);
+  if (!client_id_.empty())
+    return;
+
+  client_id_ = base::GenerateGUID();
+  local_state_->SetString(prefs::kMetricsClientID, client_id_);
+
+  if (local_state_->GetString(prefs::kMetricsOldClientID).empty()) {
+    // Record the timestamp of when the user opted in to UMA.
+    local_state_->SetInt64(prefs::kMetricsReportingEnabledTimestamp,
+                           base::Time::Now().ToTimeT());
+  } else {
+    UMA_HISTOGRAM_BOOLEAN("UMA.ClientIdMigrated", true);
+  }
+  local_state_->ClearPref(prefs::kMetricsOldClientID);
+}
+
+void MetricsStateManager::CheckForClonedInstall() {
+  DCHECK(!cloned_install_detector_);
+
+  MachineIdProvider* provider = MachineIdProvider::CreateInstance();
+  if (!provider)
+    return;
+
+  cloned_install_detector_.reset(new ClonedInstallDetector(provider));
+  cloned_install_detector_->CheckForClonedInstall(local_state_);
+}
+
+scoped_ptr<const base::FieldTrial::EntropyProvider>
+MetricsStateManager::CreateEntropyProvider() {
+  // For metrics reporting-enabled users, we combine the client ID and low
+  // entropy source to get the final entropy source. Otherwise, only use the low
+  // entropy source.
+  // This has two useful properties:
+  //  1) It makes the entropy source less identifiable for parties that do not
+  //     know the low entropy source.
+  //  2) It makes the final entropy source resettable.
+  const int low_entropy_source_value = GetLowEntropySource();
+  UMA_HISTOGRAM_SPARSE_SLOWLY("UMA.LowEntropySourceValue",
+                              low_entropy_source_value);
+  if (IsMetricsReportingEnabled()) {
+    if (entropy_source_returned_ == ENTROPY_SOURCE_NONE)
+      entropy_source_returned_ = ENTROPY_SOURCE_HIGH;
+    DCHECK_EQ(ENTROPY_SOURCE_HIGH, entropy_source_returned_);
+    const std::string high_entropy_source =
+        client_id_ + base::IntToString(low_entropy_source_value);
+    return scoped_ptr<const base::FieldTrial::EntropyProvider>(
+        new SHA1EntropyProvider(high_entropy_source));
+  }
+
+  if (entropy_source_returned_ == ENTROPY_SOURCE_NONE)
+    entropy_source_returned_ = ENTROPY_SOURCE_LOW;
+  DCHECK_EQ(ENTROPY_SOURCE_LOW, entropy_source_returned_);
+
+#if defined(OS_ANDROID) || defined(OS_IOS)
+  return scoped_ptr<const base::FieldTrial::EntropyProvider>(
+      new CachingPermutedEntropyProvider(local_state_,
+                                         low_entropy_source_value,
+                                         kMaxLowEntropySize));
+#else
+  return scoped_ptr<const base::FieldTrial::EntropyProvider>(
+      new PermutedEntropyProvider(low_entropy_source_value,
+                                  kMaxLowEntropySize));
+#endif
+}
+
+// static
+scoped_ptr<MetricsStateManager> MetricsStateManager::Create(
+    PrefService* local_state) {
+  scoped_ptr<MetricsStateManager> result;
+  // Note: |instance_exists_| is updated in the constructor and destructor.
+  if (!instance_exists_)
+    result.reset(new MetricsStateManager(local_state));
+  return result.Pass();
+}
+
+// static
+void MetricsStateManager::RegisterPrefs(PrefRegistrySimple* registry) {
+  registry->RegisterBooleanPref(prefs::kMetricsResetIds, false);
+  registry->RegisterStringPref(prefs::kMetricsClientID, std::string());
+  registry->RegisterInt64Pref(prefs::kMetricsReportingEnabledTimestamp, 0);
+  registry->RegisterIntegerPref(prefs::kMetricsLowEntropySource,
+                                kLowEntropySourceNotSet);
+
+  ClonedInstallDetector::RegisterPrefs(registry);
+  CachingPermutedEntropyProvider::RegisterPrefs(registry);
+
+  // TODO(asvitkine): Remove these once a couple of releases have passed.
+  // http://crbug.com/357704
+  registry->RegisterStringPref(prefs::kMetricsOldClientID, std::string());
+  registry->RegisterIntegerPref(prefs::kMetricsOldLowEntropySource, 0);
+}
+
+int MetricsStateManager::GetLowEntropySource() {
+  // Note that the default value for the low entropy source and the default pref
+  // value are both kLowEntropySourceNotSet, which is used to identify if the
+  // value has been set or not.
+  if (low_entropy_source_ != kLowEntropySourceNotSet)
+    return low_entropy_source_;
+
+  const CommandLine* command_line(CommandLine::ForCurrentProcess());
+  // Only try to load the value from prefs if the user did not request a reset.
+  // Otherwise, skip to generating a new value.
+  if (!command_line->HasSwitch(switches::kResetVariationState)) {
+    int value = local_state_->GetInteger(prefs::kMetricsLowEntropySource);
+    // If the value is outside the [0, kMaxLowEntropySize) range, re-generate
+    // it below.
+    if (value >= 0 && value < kMaxLowEntropySize) {
+      low_entropy_source_ = value;
+      UMA_HISTOGRAM_BOOLEAN("UMA.GeneratedLowEntropySource", false);
+      return low_entropy_source_;
+    }
+  }
+
+  UMA_HISTOGRAM_BOOLEAN("UMA.GeneratedLowEntropySource", true);
+  low_entropy_source_ = GenerateLowEntropySource();
+  local_state_->SetInteger(prefs::kMetricsLowEntropySource,
+                           low_entropy_source_);
+  local_state_->ClearPref(prefs::kMetricsOldLowEntropySource);
+  metrics::CachingPermutedEntropyProvider::ClearCache(local_state_);
+
+  return low_entropy_source_;
+}
+
+void MetricsStateManager::ResetMetricsIDsIfNecessary() {
+  if (!local_state_->GetBoolean(prefs::kMetricsResetIds))
+    return;
+
+  UMA_HISTOGRAM_BOOLEAN("UMA.MetricsIDsReset", true);
+
+  DCHECK(client_id_.empty());
+  DCHECK_EQ(kLowEntropySourceNotSet, low_entropy_source_);
+
+  local_state_->ClearPref(prefs::kMetricsClientID);
+  local_state_->ClearPref(prefs::kMetricsLowEntropySource);
+  local_state_->ClearPref(prefs::kMetricsResetIds);
+}
+
+}  // namespace metrics