/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "nsRFPService.h"

#include <algorithm>
#include <time.h>

#include "mozilla/ClearOnShutdown.h"
#include "mozilla/Logging.h"
#include "mozilla/Preferences.h"
#include "mozilla/Services.h"
#include "mozilla/StaticPtr.h"
#include "mozilla/TextEvents.h"

#include "nsCOMPtr.h"
#include "nsCoord.h"
#include "nsServiceManagerUtils.h"
#include "nsString.h"
#include "nsXULAppAPI.h"
#include "nsPrintfCString.h"

#include "nsIObserverService.h"
#include "nsIPrefBranch.h"
#include "nsIPrefService.h"
#include "nsIXULAppInfo.h"
#include "nsIXULRuntime.h"
#include "nsJSUtils.h"

#include "prenv.h"

#include "js/Date.h"

using namespace mozilla;
using namespace std;

#ifdef DEBUG
static mozilla::LazyLogModule gResistFingerprintingLog("nsResistFingerprinting");
#endif

#define RESIST_FINGERPRINTING_PREF "privacy.resistFingerprinting"
#define RFP_TIMER_PREF "privacy.reduceTimerPrecision"
#define RFP_TIMER_VALUE_PREF "privacy.resistFingerprinting.reduceTimerPrecision.microseconds"
#define RFP_TIMER_VALUE_DEFAULT 20
#define RFP_SPOOFED_FRAMES_PER_SEC_PREF "privacy.resistFingerprinting.video_frames_per_sec"
#define RFP_SPOOFED_DROPPED_RATIO_PREF  "privacy.resistFingerprinting.video_dropped_ratio"
#define RFP_TARGET_VIDEO_RES_PREF "privacy.resistFingerprinting.target_video_res"
#define RFP_SPOOFED_FRAMES_PER_SEC_DEFAULT 30
#define RFP_SPOOFED_DROPPED_RATIO_DEFAULT  5
#define RFP_TARGET_VIDEO_RES_DEFAULT 480
#define PROFILE_INITIALIZED_TOPIC "profile-initial-state"

#define RFP_DEFAULT_SPOOFING_KEYBOARD_LANG KeyboardLang::EN
#define RFP_DEFAULT_SPOOFING_KEYBOARD_REGION KeyboardRegion::US

NS_IMPL_ISUPPORTS(nsRFPService, nsIObserver)

static StaticRefPtr<nsRFPService> sRFPService;
static bool sInitialized = false;
Atomic<bool, ReleaseAcquire> nsRFPService::sPrivacyResistFingerprinting;
Atomic<bool, ReleaseAcquire> nsRFPService::sPrivacyTimerPrecisionReduction;
// Note: anytime you want to use this variable, you should probably use TimerResolution() instead
Atomic<uint32_t, ReleaseAcquire> sResolutionUSec;
static uint32_t sVideoFramesPerSec;
static uint32_t sVideoDroppedRatio;
static uint32_t sTargetVideoRes;
nsDataHashtable<KeyboardHashKey, const SpoofingKeyboardCode*>*
  nsRFPService::sSpoofingKeyboardCodes = nullptr;

/* static */
nsRFPService*
nsRFPService::GetOrCreate()
{
  if (!sInitialized) {
    sRFPService = new nsRFPService();
    nsresult rv = sRFPService->Init();

    if (NS_FAILED(rv)) {
      sRFPService = nullptr;
      return nullptr;
    }

    ClearOnShutdown(&sRFPService);
    sInitialized = true;
  }

  return sRFPService;
}

inline double
TimerResolution()
{
  if(nsRFPService::IsResistFingerprintingEnabled()) {
    return max(100000.0, (double)sResolutionUSec);
  }
  return sResolutionUSec;
}

/* static */
bool
nsRFPService::IsResistFingerprintingEnabled()
{
  return sPrivacyResistFingerprinting;
}

/* static */
bool
nsRFPService::IsTimerPrecisionReductionEnabled()
{
  return (sPrivacyTimerPrecisionReduction || IsResistFingerprintingEnabled()) &&
         TimerResolution() != 0;
}

/* static */
double
nsRFPService::ReduceTimePrecisionAsMSecs(double aTime)
{
  if (!IsTimerPrecisionReductionEnabled()) {
    return aTime;
  }
  const double resolutionMSec = TimerResolution() / 1000.0;
  double ret = floor(aTime / resolutionMSec) * resolutionMSec;
#if defined(DEBUG)
  MOZ_LOG(gResistFingerprintingLog, LogLevel::Verbose,
    ("Given: %.*f, Rounding with %.*f, Intermediate: %.*f, Got: %.*f",
      DBL_DIG-1, aTime, DBL_DIG-1, resolutionMSec, DBL_DIG-1, floor(aTime / resolutionMSec), DBL_DIG-1, ret));
#endif
  return ret;
}

/* static */
double
nsRFPService::ReduceTimePrecisionAsUSecs(double aTime)
{
  if (!IsTimerPrecisionReductionEnabled()) {
    return aTime;
  }
  double resolutionUSec = TimerResolution();
  double ret = floor(aTime / resolutionUSec) * resolutionUSec;
#if defined(DEBUG)
  double tmp_sResolutionUSec = resolutionUSec;
  MOZ_LOG(gResistFingerprintingLog, LogLevel::Verbose,
    ("Given: %.*f, Rounding with %.*f, Intermediate: %.*f, Got: %.*f",
      DBL_DIG-1, aTime, DBL_DIG-1, tmp_sResolutionUSec, DBL_DIG-1, floor(aTime / tmp_sResolutionUSec), DBL_DIG-1, ret));
#endif
  return ret;
}

/* static */
uint32_t
nsRFPService::CalculateTargetVideoResolution(uint32_t aVideoQuality)
{
  return aVideoQuality * NSToIntCeil(aVideoQuality * 16 / 9.0);
}

/* static */
double
nsRFPService::ReduceTimePrecisionAsSecs(double aTime)
{
  if (!IsTimerPrecisionReductionEnabled()) {
    return aTime;
  }
  double resolutionUSec = TimerResolution();
  if (TimerResolution() < 1000000) {
    // The resolution is smaller than one sec.  Use the reciprocal to avoid
    // floating point error.
    const double resolutionSecReciprocal = 1000000.0 / resolutionUSec;
    double ret = floor(aTime * resolutionSecReciprocal) / resolutionSecReciprocal;
#if defined(DEBUG)
  MOZ_LOG(gResistFingerprintingLog, LogLevel::Verbose,
    ("Given: %.*f, Reciprocal Rounding with %.*f, Intermediate: %.*f, Got: %.*f",
      DBL_DIG-1, aTime, DBL_DIG-1, resolutionSecReciprocal, DBL_DIG-1, floor(aTime * resolutionSecReciprocal), DBL_DIG-1, ret));
#endif
    return ret;
  }
  const double resolutionSec = resolutionUSec / 1000000.0;
  double ret = floor(aTime / resolutionSec) * resolutionSec;
#if defined(DEBUG)
  MOZ_LOG(gResistFingerprintingLog, LogLevel::Verbose,
    ("Given: %.*f, Rounding with %.*f, Intermediate: %.*f, Got: %.*f",
      DBL_DIG-1, aTime, DBL_DIG-1, resolutionSec, DBL_DIG-1, floor(aTime / resolutionSec), DBL_DIG-1, ret));
#endif
  return ret;
}

/* static */
uint32_t
nsRFPService::GetSpoofedTotalFrames(double aTime)
{
  double time = ReduceTimePrecisionAsSecs(aTime);

  return NSToIntFloor(time * sVideoFramesPerSec);
}

/* static */
uint32_t
nsRFPService::GetSpoofedDroppedFrames(double aTime, uint32_t aWidth, uint32_t aHeight)
{
  uint32_t targetRes = CalculateTargetVideoResolution(sTargetVideoRes);

  // The video resolution is less than or equal to the target resolution, we
  // report a zero dropped rate for this case.
  if (targetRes >= aWidth * aHeight) {
    return 0;
  }

  double time = ReduceTimePrecisionAsSecs(aTime);
  // Bound the dropped ratio from 0 to 100.
  uint32_t boundedDroppedRatio = min(sVideoDroppedRatio, 100u);

  return NSToIntFloor(time * sVideoFramesPerSec * (boundedDroppedRatio / 100.0));
}

/* static */
uint32_t
nsRFPService::GetSpoofedPresentedFrames(double aTime, uint32_t aWidth, uint32_t aHeight)
{
  uint32_t targetRes = CalculateTargetVideoResolution(sTargetVideoRes);

  // The target resolution is greater than the current resolution. For this case,
  // there will be no dropped frames, so we report total frames directly.
  if (targetRes >= aWidth * aHeight) {
    return GetSpoofedTotalFrames(aTime);
  }

  double time = ReduceTimePrecisionAsSecs(aTime);
  // Bound the dropped ratio from 0 to 100.
  uint32_t boundedDroppedRatio = min(sVideoDroppedRatio, 100u);

  return NSToIntFloor(time * sVideoFramesPerSec * ((100 - boundedDroppedRatio) / 100.0));
}

/* static */
nsresult
nsRFPService::GetSpoofedUserAgent(nsACString &userAgent)
{
  // This function generates the spoofed value of User Agent.
  // We spoof the values of the platform and Firefox version, which could be
  // used as fingerprinting sources to identify individuals.
  // Reference of the format of User Agent:
  // https://developer.mozilla.org/en-US/docs/Web/API/NavigatorID/userAgent
  // https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/User-Agent

  nsresult rv;
  nsCOMPtr<nsIXULAppInfo> appInfo =
    do_GetService("@mozilla.org/xre/app-info;1", &rv);
  NS_ENSURE_SUCCESS(rv, rv);

  nsAutoCString appVersion;
  rv = appInfo->GetVersion(appVersion);
  NS_ENSURE_SUCCESS(rv, rv);

  // The browser version will be spoofed as the last ESR version.
  // By doing so, the anonymity group will cover more versions instead of one
  // version.
  uint32_t firefoxVersion = appVersion.ToInteger(&rv);
  NS_ENSURE_SUCCESS(rv, rv);

  // Starting from Firefox 10, Firefox ESR was released once every seven
  // Firefox releases, e.g. Firefox 10, 17, 24, 31, and so on.
  // We infer the last and closest ESR version based on this rule.
  nsCOMPtr<nsIXULRuntime> runtime =
    do_GetService("@mozilla.org/xre/runtime;1", &rv);
  NS_ENSURE_SUCCESS(rv, rv);

  nsAutoCString updateChannel;
  rv = runtime->GetDefaultUpdateChannel(updateChannel);
  NS_ENSURE_SUCCESS(rv, rv);

  // If we are running in Firefox ESR, determine whether the formula of ESR
  // version has changed.  Once changed, we must update the formula in this
  // function.
  if (updateChannel.EqualsLiteral("esr")) {
    MOZ_ASSERT(((firefoxVersion % 7) == 3),
      "Please udpate ESR version formula in nsRFPService.cpp");
  }

  uint32_t spoofedVersion = firefoxVersion - ((firefoxVersion - 3) % 7);
  userAgent.Assign(nsPrintfCString(
    "Mozilla/5.0 (%s; rv:%d.0) Gecko/%s Firefox/%d.0",
    SPOOFED_UA_OS, spoofedVersion, LEGACY_BUILD_ID, spoofedVersion));

  return rv;
}

nsresult
nsRFPService::Init()
{
  MOZ_ASSERT(NS_IsMainThread());

  nsresult rv;

  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
  NS_ENSURE_TRUE(obs, NS_ERROR_NOT_AVAILABLE);

  rv = obs->AddObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID, false);
  NS_ENSURE_SUCCESS(rv, rv);

#if defined(XP_WIN)
  rv = obs->AddObserver(this, PROFILE_INITIALIZED_TOPIC, false);
  NS_ENSURE_SUCCESS(rv, rv);
#endif

  nsCOMPtr<nsIPrefBranch> prefs = do_GetService(NS_PREFSERVICE_CONTRACTID);
  NS_ENSURE_TRUE(prefs, NS_ERROR_NOT_AVAILABLE);

  rv = prefs->AddObserver(RESIST_FINGERPRINTING_PREF, this, false);
  NS_ENSURE_SUCCESS(rv, rv);

  rv = prefs->AddObserver(RFP_TIMER_PREF, this, false);
  NS_ENSURE_SUCCESS(rv, rv);

  rv = prefs->AddObserver(RFP_TIMER_VALUE_PREF, this, false);
  NS_ENSURE_SUCCESS(rv, rv);

  Preferences::AddAtomicBoolVarCache(&sPrivacyTimerPrecisionReduction,
                                     RFP_TIMER_PREF,
                                     true);

  Preferences::AddAtomicUintVarCache(&sResolutionUSec,
                                     RFP_TIMER_VALUE_PREF,
                                     RFP_TIMER_VALUE_DEFAULT);
  Preferences::AddUintVarCache(&sVideoFramesPerSec,
                               RFP_SPOOFED_FRAMES_PER_SEC_PREF,
                               RFP_SPOOFED_FRAMES_PER_SEC_DEFAULT);
  Preferences::AddUintVarCache(&sVideoDroppedRatio,
                               RFP_SPOOFED_DROPPED_RATIO_PREF,
                               RFP_SPOOFED_DROPPED_RATIO_DEFAULT);
  Preferences::AddUintVarCache(&sTargetVideoRes,
                               RFP_TARGET_VIDEO_RES_PREF,
                               RFP_TARGET_VIDEO_RES_DEFAULT);

  // We backup the original TZ value here.
  const char* tzValue = PR_GetEnv("TZ");
  if (tzValue) {
    mInitialTZValue = nsCString(tzValue);
  }

  // Call Update here to cache the values of the prefs and set the timezone.
  UpdateRFPPref();

  return rv;
}

// This function updates only timing-related fingerprinting items
void
nsRFPService::UpdateTimers() {
  MOZ_ASSERT(NS_IsMainThread());

  if (sPrivacyResistFingerprinting || sPrivacyTimerPrecisionReduction) {
    JS::SetTimeResolutionUsec(TimerResolution());
  } else if (sInitialized) {
    JS::SetTimeResolutionUsec(0);
  }
}


// This function updates every fingerprinting item necessary except timing-related
void
nsRFPService::UpdateRFPPref()
{
  MOZ_ASSERT(NS_IsMainThread());
  sPrivacyResistFingerprinting = Preferences::GetBool(RESIST_FINGERPRINTING_PREF);

  UpdateTimers();

  if (sPrivacyResistFingerprinting) {
    PR_SetEnv("TZ=UTC");
  } else if (sInitialized) {
    // We will not touch the TZ value if 'privacy.resistFingerprinting' is false during
    // the time of initialization.
    if (!mInitialTZValue.IsEmpty()) {
      nsAutoCString tzValue = NS_LITERAL_CSTRING("TZ=") + mInitialTZValue;
      static char* tz = nullptr;

      // If the tz has been set before, we free it first since it will be allocated
      // a new value later.
      if (tz) {
        free(tz);
      }
      // PR_SetEnv() needs the input string been leaked intentionally, so
      // we copy it here.
      tz = ToNewCString(tzValue);
      if (tz) {
        PR_SetEnv(tz);
      }
    } else {
#if defined(XP_WIN)
      // For Windows, we reset the TZ to an empty string. This will make Windows to use
      // its system timezone.
      PR_SetEnv("TZ=");
#else
      // For POSIX like system, we reset the TZ to the /etc/localtime, which is the
      // system timezone.
      PR_SetEnv("TZ=:/etc/localtime");
#endif
    }
  }

  nsJSUtils::ResetTimeZone();
}

void
nsRFPService::StartShutdown()
{
  MOZ_ASSERT(NS_IsMainThread());

  nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();

  if (obs) {
    obs->RemoveObserver(this, NS_XPCOM_SHUTDOWN_OBSERVER_ID);

    nsCOMPtr<nsIPrefBranch> prefs = do_GetService(NS_PREFSERVICE_CONTRACTID);

    if (prefs) {
      prefs->RemoveObserver(RESIST_FINGERPRINTING_PREF, this);
      prefs->RemoveObserver(RFP_TIMER_PREF, this);
      prefs->RemoveObserver(RFP_TIMER_VALUE_PREF, this);
    }
  }
}

/* static */
void
nsRFPService::MaybeCreateSpoofingKeyCodes(const KeyboardLangs aLang,
                                          const KeyboardRegions aRegion)
{
  if (!sSpoofingKeyboardCodes) {
    sSpoofingKeyboardCodes =
      new nsDataHashtable<KeyboardHashKey, const SpoofingKeyboardCode*>();
  }

  if (KeyboardLang::EN == aLang) {
    switch (aRegion) {
      case KeyboardRegion::US:
        MaybeCreateSpoofingKeyCodesForEnUS();
        break;
    }
  }
}

/* static */
void
nsRFPService::MaybeCreateSpoofingKeyCodesForEnUS()
{
  MOZ_ASSERT(sSpoofingKeyboardCodes);

  static bool sInitialized = false;
  const KeyboardLangs lang = KeyboardLang::EN;
  const KeyboardRegions reg = KeyboardRegion::US;

  if (sInitialized) {
    return;
  }

  static const SpoofingKeyboardInfo spoofingKeyboardInfoTable[] = {
#define KEY(key_, _codeNameIdx, _keyCode, _modifier) \
    { KEY_NAME_INDEX_USE_STRING, NS_LITERAL_STRING(key_), \
      { CODE_NAME_INDEX_##_codeNameIdx, _keyCode, _modifier } },
#define CONTROL(keyNameIdx_, _codeNameIdx, _keyCode) \
    { KEY_NAME_INDEX_##keyNameIdx_, EmptyString(), \
      { CODE_NAME_INDEX_##_codeNameIdx, _keyCode, MODIFIER_NONE } },
#include "KeyCodeConsensus_En_US.h"
#undef CONTROL
#undef KEY
  };

  for (const auto& keyboardInfo : spoofingKeyboardInfoTable) {
    KeyboardHashKey key(lang, reg,
                        keyboardInfo.mKeyIdx,
                        keyboardInfo.mKey);
    MOZ_ASSERT(!sSpoofingKeyboardCodes->Lookup(key),
               "Double-defining key code; fix your KeyCodeConsensus file");
    sSpoofingKeyboardCodes->Put(key, &keyboardInfo.mSpoofingCode);
  }

  sInitialized = true;
}

/* static */
void
nsRFPService::GetKeyboardLangAndRegion(const nsAString& aLanguage,
                                       KeyboardLangs& aLocale,
                                       KeyboardRegions& aRegion)
{
  nsAutoString langStr;
  nsAutoString regionStr;
  uint32_t partNum = 0;

  for (const nsAString& part : aLanguage.Split('-')) {
    if (partNum == 0) {
      langStr = part;
    } else {
      regionStr = part;
      break;
    }

    partNum++;
  }

  // We test each language here as well as the region. There are some cases that
  // only the language is given, we will use the default region code when this
  // happens. The default region should depend on the given language.
  if (langStr.EqualsLiteral(RFP_KEYBOARD_LANG_STRING_EN)) {
    aLocale = KeyboardLang::EN;
    // Give default values first.
    aRegion = KeyboardRegion::US;

    if (regionStr.EqualsLiteral(RFP_KEYBOARD_REGION_STRING_US)) {
      aRegion = KeyboardRegion::US;
    }
  } else {
    // There is no spoofed keyboard locale for the given language. We use the
    // default one in this case.
    aLocale = RFP_DEFAULT_SPOOFING_KEYBOARD_LANG;
    aRegion = RFP_DEFAULT_SPOOFING_KEYBOARD_REGION;
  }
}

/* static */
bool
nsRFPService::GetSpoofedKeyCodeInfo(const nsIDocument* aDoc,
                                    const WidgetKeyboardEvent* aKeyboardEvent,
                                    SpoofingKeyboardCode& aOut)
{
  MOZ_ASSERT(aKeyboardEvent);

  KeyboardLangs keyboardLang = RFP_DEFAULT_SPOOFING_KEYBOARD_LANG;
  KeyboardRegions keyboardRegion = RFP_DEFAULT_SPOOFING_KEYBOARD_REGION;
  // If the document is given, we use the content language which is get from the
  // document. Otherwise, we use the default one.
  if (aDoc) {
    nsAutoString language;
    aDoc->GetContentLanguage(language);

    // If the content-langauge is not given, we try to get langauge from the HTML
    // lang attribute.
    if (language.IsEmpty()) {
      Element* elm = aDoc->GetHtmlElement();

      if (elm) {
        elm->GetLang(language);
      }
    }

    // If two or more languages are given, per HTML5 spec, we should consider
    // it as 'unknown'. So we use the default one.
    if (!language.IsEmpty() &&
        !language.Contains(char16_t(','))) {
      language.StripWhitespace();
      GetKeyboardLangAndRegion(language, keyboardLang,
                               keyboardRegion);
    }
  }

  MaybeCreateSpoofingKeyCodes(keyboardLang, keyboardRegion);

  KeyNameIndex keyIdx = aKeyboardEvent->mKeyNameIndex;
  nsAutoString keyName;

  if (keyIdx == KEY_NAME_INDEX_USE_STRING) {
    keyName = aKeyboardEvent->mKeyValue;
  }

  KeyboardHashKey key(keyboardLang, keyboardRegion, keyIdx, keyName);
  const SpoofingKeyboardCode* keyboardCode = sSpoofingKeyboardCodes->Get(key);

  if (keyboardCode) {
    aOut = *keyboardCode;
    return true;
  }

  return false;
}

/* static */
bool
nsRFPService::GetSpoofedModifierStates(const nsIDocument* aDoc,
                                       const WidgetKeyboardEvent* aKeyboardEvent,
                                       const Modifiers aModifier,
                                       bool& aOut)
{
  MOZ_ASSERT(aKeyboardEvent);

  // For modifier or control keys, we don't need to hide its modifier states.
  if (aKeyboardEvent->mKeyNameIndex != KEY_NAME_INDEX_USE_STRING) {
    return false;
  }

  // We will spoof the modifer state for Alt, Shift, AltGraph and Control.
  if (aModifier & (MODIFIER_ALT | MODIFIER_SHIFT | MODIFIER_ALTGRAPH | MODIFIER_CONTROL)) {
    SpoofingKeyboardCode keyCodeInfo;

    if (GetSpoofedKeyCodeInfo(aDoc, aKeyboardEvent, keyCodeInfo)) {
      aOut = keyCodeInfo.mModifierStates & aModifier;
      return true;
    }
  }

  return false;
}

/* static */
bool
nsRFPService::GetSpoofedCode(const nsIDocument* aDoc,
                             const WidgetKeyboardEvent* aKeyboardEvent,
                             nsAString& aOut)
{
  MOZ_ASSERT(aKeyboardEvent);

  SpoofingKeyboardCode keyCodeInfo;

  if (!GetSpoofedKeyCodeInfo(aDoc, aKeyboardEvent, keyCodeInfo)) {
    return false;
  }

  WidgetKeyboardEvent::GetDOMCodeName(keyCodeInfo.mCode, aOut);

  // We need to change the 'Left' with 'Right' if the location indicates
  // it's a right key.
  if (aKeyboardEvent->mLocation == nsIDOMKeyEvent::DOM_KEY_LOCATION_RIGHT &&
      StringEndsWith(aOut, NS_LITERAL_STRING("Left"))) {
    aOut.ReplaceLiteral(aOut.Length() - 4, 4, u"Right");
  }

  return true;
}

/* static */
bool
nsRFPService::GetSpoofedKeyCode(const nsIDocument* aDoc,
                                const WidgetKeyboardEvent* aKeyboardEvent,
                                uint32_t& aOut)
{
  MOZ_ASSERT(aKeyboardEvent);

  SpoofingKeyboardCode keyCodeInfo;

  if (GetSpoofedKeyCodeInfo(aDoc, aKeyboardEvent, keyCodeInfo)) {
    aOut = keyCodeInfo.mKeyCode;
    return true;
  }

  return false;
}

NS_IMETHODIMP
nsRFPService::Observe(nsISupports* aObject, const char* aTopic,
                      const char16_t* aMessage)
{
  if (!strcmp(NS_PREFBRANCH_PREFCHANGE_TOPIC_ID, aTopic)) {
    NS_ConvertUTF16toUTF8 pref(aMessage);

    if (pref.EqualsLiteral(RFP_TIMER_PREF) || pref.EqualsLiteral(RFP_TIMER_VALUE_PREF)) {
      UpdateTimers();
    }
    else if (pref.EqualsLiteral(RESIST_FINGERPRINTING_PREF)) {
      UpdateRFPPref();

#if defined(XP_WIN)
      if (!XRE_IsE10sParentProcess()) {
        // Windows does not follow POSIX. Updates to the TZ environment variable
        // are not reflected immediately on that platform as they are on UNIX
        // systems without this call.
        _tzset();
      }
#endif
    }
  }

  if (!strcmp(NS_XPCOM_SHUTDOWN_OBSERVER_ID, aTopic)) {
    StartShutdown();
  }
#if defined(XP_WIN)
  else if (!strcmp(PROFILE_INITIALIZED_TOPIC, aTopic)) {
    // If we're e10s, then we don't need to run this, since the child process will
    // simply inherit the environment variable from the parent process, in which
    // case it's unnecessary to call _tzset().
    if (XRE_IsParentProcess() && !XRE_IsE10sParentProcess()) {
      // Windows does not follow POSIX. Updates to the TZ environment variable
      // are not reflected immediately on that platform as they are on UNIX
      // systems without this call.
      _tzset();
    }

    nsCOMPtr<nsIObserverService> obs = mozilla::services::GetObserverService();
    NS_ENSURE_TRUE(obs, NS_ERROR_NOT_AVAILABLE);

    nsresult rv = obs->RemoveObserver(this, PROFILE_INITIALIZED_TOPIC);
    NS_ENSURE_SUCCESS(rv, rv);
  }
#endif

  return NS_OK;
}