Add explicit TimeDelta constexpr copy constructor.

base/time/time.h

Index: base/time/time.h
diff --git a/base/time/time.h b/base/time/time.h
index be0eb20f88a4df500d5dfe289fc0d35fed6acd64..b09cd9ef8d09e55c1d13a3101fb25bcb51552df9 100644
--- a/base/time/time.h
+++ b/base/time/time.h
@@ -1,839 +1,844 @@
-// 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.
-
-// Time represents an absolute point in coordinated universal time (UTC),
-// internally represented as microseconds (s/1,000,000) since the Windows epoch
-// (1601-01-01 00:00:00 UTC). System-dependent clock interface routines are
-// defined in time_PLATFORM.cc. Note that values for Time may skew and jump
-// around as the operating system makes adjustments to synchronize (e.g., with
-// NTP servers). Thus, client code that uses the Time class must account for
-// this.
-//
-// TimeDelta represents a duration of time, internally represented in
-// microseconds.
-//
-// TimeTicks and ThreadTicks represent an abstract time that is most of the time
-// incrementing, for use in measuring time durations. Internally, they are
-// represented in microseconds. They can not be converted to a human-readable
-// time, but are guaranteed not to decrease (unlike the Time class). Note that
-// TimeTicks may "stand still" (e.g., if the computer is suspended), and
-// ThreadTicks will "stand still" whenever the thread has been de-scheduled by
-// the operating system.
-//
-// All time classes are copyable, assignable, and occupy 64-bits per
-// instance. Thus, they can be efficiently passed by-value (as opposed to
-// by-reference).
-//
-// Definitions of operator<< are provided to make these types work with
-// DCHECK_EQ() and other log macros. For human-readable formatting, see
-// "base/i18n/time_formatting.h".
-//
-// So many choices!  Which time class should you use?  Examples:
-//
-//   Time:        Interpreting the wall-clock time provided by a remote
-//                system. Detecting whether cached resources have
-//                expired. Providing the user with a display of the current date
-//                and time. Determining the amount of time between events across
-//                re-boots of the machine.
-//
-//   TimeTicks:   Tracking the amount of time a task runs. Executing delayed
-//                tasks at the right time. Computing presentation timestamps.
-//                Synchronizing audio and video using TimeTicks as a common
-//                reference clock (lip-sync). Measuring network round-trip
-//                latency.
-//
-//   ThreadTicks: Benchmarking how long the current thread has been doing actual
-//                work.
-
-#ifndef BASE_TIME_TIME_H_
-#define BASE_TIME_TIME_H_
-
-#include <stdint.h>
-#include <time.h>
-
-#include <iosfwd>
-#include <limits>
-
-#include "base/base_export.h"
-#include "base/compiler_specific.h"
-#include "base/numerics/safe_math.h"
-#include "build/build_config.h"
-
-#if defined(OS_MACOSX)
-#include <CoreFoundation/CoreFoundation.h>
-// Avoid Mac system header macro leak.
-#undef TYPE_BOOL
-#endif
-
-#if defined(OS_POSIX)
-#include <unistd.h>
-#include <sys/time.h>
-#endif
-
-#if defined(OS_WIN)
-// For FILETIME in FromFileTime, until it moves to a new converter class.
-// See TODO(iyengar) below.
-#include <windows.h>
-#include "base/gtest_prod_util.h"
-#endif
-
-namespace base {
-
-class PlatformThreadHandle;
-class TimeDelta;
-
-// The functions in the time_internal namespace are meant to be used only by the
-// time classes and functions.  Please use the math operators defined in the
-// time classes instead.
-namespace time_internal {
-
-// Add or subtract |value| from a TimeDelta. The int64_t argument and return
-// value are in terms of a microsecond timebase.
-BASE_EXPORT int64_t SaturatedAdd(TimeDelta delta, int64_t value);
-BASE_EXPORT int64_t SaturatedSub(TimeDelta delta, int64_t value);
-
-// Clamp |value| on overflow and underflow conditions. The int64_t argument and
-// return value are in terms of a microsecond timebase.
-BASE_EXPORT int64_t FromCheckedNumeric(const CheckedNumeric<int64_t> value);
-
-}  // namespace time_internal
-
-// TimeDelta ------------------------------------------------------------------
-
-class BASE_EXPORT TimeDelta {
- public:
-  TimeDelta() : delta_(0) {
-  }
-
-  // Converts units of time to TimeDeltas.
-  static constexpr TimeDelta FromDays(int days);
-  static constexpr TimeDelta FromHours(int hours);
-  static constexpr TimeDelta FromMinutes(int minutes);
-  static constexpr TimeDelta FromSeconds(int64_t secs);
-  static constexpr TimeDelta FromMilliseconds(int64_t ms);
-  static constexpr TimeDelta FromSecondsD(double secs);
-  static constexpr TimeDelta FromMillisecondsD(double ms);
-  static constexpr TimeDelta FromMicroseconds(int64_t us);
-#if defined(OS_WIN)
-  static TimeDelta FromQPCValue(LONGLONG qpc_value);
-#endif
-
-  // Converts an integer value representing TimeDelta to a class. This is used
-  // when deserializing a |TimeDelta| structure, using a value known to be
-  // compatible. It is not provided as a constructor because the integer type
-  // may be unclear from the perspective of a caller.
-  static TimeDelta FromInternalValue(int64_t delta) { return TimeDelta(delta); }
-
-  // Returns the maximum time delta, which should be greater than any reasonable
-  // time delta we might compare it to. Adding or subtracting the maximum time
-  // delta to a time or another time delta has an undefined result.
-  static TimeDelta Max();
-
-  // Returns the internal numeric value of the TimeDelta object. Please don't
-  // use this and do arithmetic on it, as it is more error prone than using the
-  // provided operators.
-  // For serializing, use FromInternalValue to reconstitute.
-  int64_t ToInternalValue() const { return delta_; }
-
-  // Returns the magnitude (absolute value) of this TimeDelta.
-  TimeDelta magnitude() const {
-    // Some toolchains provide an incomplete C++11 implementation and lack an
-    // int64_t overload for std::abs().  The following is a simple branchless
-    // implementation:
-    const int64_t mask = delta_ >> (sizeof(delta_) * 8 - 1);
-    return TimeDelta((delta_ + mask) ^ mask);
-  }
-
-  // Returns true if the time delta is zero.
-  bool is_zero() const {
-    return delta_ == 0;
-  }
-
-  // Returns true if the time delta is the maximum time delta.
-  bool is_max() const { return delta_ == std::numeric_limits<int64_t>::max(); }
-
-#if defined(OS_POSIX)
-  struct timespec ToTimeSpec() const;
-#endif
-
-  // Returns the time delta in some unit. The F versions return a floating
-  // point value, the "regular" versions return a rounded-down value.
-  //
-  // InMillisecondsRoundedUp() instead returns an integer that is rounded up
-  // to the next full millisecond.
-  int InDays() const;
-  int InHours() const;
-  int InMinutes() const;
-  double InSecondsF() const;
-  int64_t InSeconds() const;
-  double InMillisecondsF() const;
-  int64_t InMilliseconds() const;
-  int64_t InMillisecondsRoundedUp() const;
-  int64_t InMicroseconds() const;
-
-  TimeDelta& operator=(TimeDelta other) {
-    delta_ = other.delta_;
-    return *this;
-  }
-
-  // Computations with other deltas.
-  TimeDelta operator+(TimeDelta other) const {
-    return TimeDelta(time_internal::SaturatedAdd(*this, other.delta_));
-  }
-  TimeDelta operator-(TimeDelta other) const {
-    return TimeDelta(time_internal::SaturatedSub(*this, other.delta_));
-  }
-
-  TimeDelta& operator+=(TimeDelta other) {
-    return *this = (*this + other);
-  }
-  TimeDelta& operator-=(TimeDelta other) {
-    return *this = (*this - other);
-  }
-  TimeDelta operator-() const {
-    return TimeDelta(-delta_);
-  }
-
-  // Computations with numeric types.
-  template<typename T>
-  TimeDelta operator*(T a) const {
-    CheckedNumeric<int64_t> rv(delta_);
-    rv *= a;
-    return TimeDelta(time_internal::FromCheckedNumeric(rv));
-  }
-  template<typename T>
-  TimeDelta operator/(T a) const {
-    CheckedNumeric<int64_t> rv(delta_);
-    rv /= a;
-    return TimeDelta(time_internal::FromCheckedNumeric(rv));
-  }
-  template<typename T>
-  TimeDelta& operator*=(T a) {
-    return *this = (*this * a);
-  }
-  template<typename T>
-  TimeDelta& operator/=(T a) {
-    return *this = (*this / a);
-  }
-
-  int64_t operator/(TimeDelta a) const { return delta_ / a.delta_; }
-  TimeDelta operator%(TimeDelta a) const {
-    return TimeDelta(delta_ % a.delta_);
-  }
-
-  // Comparison operators.
-  constexpr bool operator==(TimeDelta other) const {
-    return delta_ == other.delta_;
-  }
-  constexpr bool operator!=(TimeDelta other) const {
-    return delta_ != other.delta_;
-  }
-  constexpr bool operator<(TimeDelta other) const {
-    return delta_ < other.delta_;
-  }
-  constexpr bool operator<=(TimeDelta other) const {
-    return delta_ <= other.delta_;
-  }
-  constexpr bool operator>(TimeDelta other) const {
-    return delta_ > other.delta_;
-  }
-  constexpr bool operator>=(TimeDelta other) const {
-    return delta_ >= other.delta_;
-  }
-
- private:
-  friend int64_t time_internal::SaturatedAdd(TimeDelta delta, int64_t value);
-  friend int64_t time_internal::SaturatedSub(TimeDelta delta, int64_t value);
-
-  // Constructs a delta given the duration in microseconds. This is private
-  // to avoid confusion by callers with an integer constructor. Use
-  // FromSeconds, FromMilliseconds, etc. instead.
-  constexpr explicit TimeDelta(int64_t delta_us) : delta_(delta_us) {}
-
-  // Private method to build a delta from a double.
-  static constexpr TimeDelta FromDouble(double value);
-
-  // Private method to build a delta from the product of a user-provided value
-  // and a known-positive value.
-  static constexpr TimeDelta FromProduct(int64_t value, int64_t positive_value);
-
-  // Delta in microseconds.
-  int64_t delta_;
-};
-
-template<typename T>
-inline TimeDelta operator*(T a, TimeDelta td) {
-  return td * a;
-}
-
-// For logging use only.
-BASE_EXPORT std::ostream& operator<<(std::ostream& os, TimeDelta time_delta);
-
-// Do not reference the time_internal::TimeBase template class directly.  Please
-// use one of the time subclasses instead, and only reference the public
-// TimeBase members via those classes.
-namespace time_internal {
-
-// TimeBase--------------------------------------------------------------------
-
-// Provides value storage and comparison/math operations common to all time
-// classes. Each subclass provides for strong type-checking to ensure
-// semantically meaningful comparison/math of time values from the same clock
-// source or timeline.
-template<class TimeClass>
-class TimeBase {
- public:
-  static const int64_t kHoursPerDay = 24;
-  static const int64_t kMillisecondsPerSecond = 1000;
-  static const int64_t kMillisecondsPerDay =
-      kMillisecondsPerSecond * 60 * 60 * kHoursPerDay;
-  static const int64_t kMicrosecondsPerMillisecond = 1000;
-  static const int64_t kMicrosecondsPerSecond =
-      kMicrosecondsPerMillisecond * kMillisecondsPerSecond;
-  static const int64_t kMicrosecondsPerMinute = kMicrosecondsPerSecond * 60;
-  static const int64_t kMicrosecondsPerHour = kMicrosecondsPerMinute * 60;
-  static const int64_t kMicrosecondsPerDay =
-      kMicrosecondsPerHour * kHoursPerDay;
-  static const int64_t kMicrosecondsPerWeek = kMicrosecondsPerDay * 7;
-  static const int64_t kNanosecondsPerMicrosecond = 1000;
-  static const int64_t kNanosecondsPerSecond =
-      kNanosecondsPerMicrosecond * kMicrosecondsPerSecond;
-
-  // Returns true if this object has not been initialized.
-  //
-  // Warning: Be careful when writing code that performs math on time values,
-  // since it's possible to produce a valid "zero" result that should not be
-  // interpreted as a "null" value.
-  bool is_null() const {
-    return us_ == 0;
-  }
-
-  // Returns true if this object represents the maximum time.
-  bool is_max() const { return us_ == std::numeric_limits<int64_t>::max(); }
-
-  // Returns the maximum time, which should be greater than any reasonable time
-  // with which we might compare it.
-  static TimeClass Max() {
-    return TimeClass(std::numeric_limits<int64_t>::max());
-  }
-
-  // For serializing only. Use FromInternalValue() to reconstitute. Please don't
-  // use this and do arithmetic on it, as it is more error prone than using the
-  // provided operators.
-  int64_t ToInternalValue() const { return us_; }
-
-  TimeClass& operator=(TimeClass other) {
-    us_ = other.us_;
-    return *(static_cast<TimeClass*>(this));
-  }
-
-  // Compute the difference between two times.
-  TimeDelta operator-(TimeClass other) const {
-    return TimeDelta::FromMicroseconds(us_ - other.us_);
-  }
-
-  // Return a new time modified by some delta.
-  TimeClass operator+(TimeDelta delta) const {
-    return TimeClass(time_internal::SaturatedAdd(delta, us_));
-  }
-  TimeClass operator-(TimeDelta delta) const {
-    return TimeClass(-time_internal::SaturatedSub(delta, us_));
-  }
-
-  // Modify by some time delta.
-  TimeClass& operator+=(TimeDelta delta) {
-    return static_cast<TimeClass&>(*this = (*this + delta));
-  }
-  TimeClass& operator-=(TimeDelta delta) {
-    return static_cast<TimeClass&>(*this = (*this - delta));
-  }
-
-  // Comparison operators
-  bool operator==(TimeClass other) const {
-    return us_ == other.us_;
-  }
-  bool operator!=(TimeClass other) const {
-    return us_ != other.us_;
-  }
-  bool operator<(TimeClass other) const {
-    return us_ < other.us_;
-  }
-  bool operator<=(TimeClass other) const {
-    return us_ <= other.us_;
-  }
-  bool operator>(TimeClass other) const {
-    return us_ > other.us_;
-  }
-  bool operator>=(TimeClass other) const {
-    return us_ >= other.us_;
-  }
-
-  // Converts an integer value representing TimeClass to a class. This is used
-  // when deserializing a |TimeClass| structure, using a value known to be
-  // compatible. It is not provided as a constructor because the integer type
-  // may be unclear from the perspective of a caller.
-  static TimeClass FromInternalValue(int64_t us) { return TimeClass(us); }
-
- protected:
-  explicit TimeBase(int64_t us) : us_(us) {}
-
-  // Time value in a microsecond timebase.
-  int64_t us_;
-};
-
-}  // namespace time_internal
-
-template<class TimeClass>
-inline TimeClass operator+(TimeDelta delta, TimeClass t) {
-  return t + delta;
-}
-
-// Time -----------------------------------------------------------------------
-
-// Represents a wall clock time in UTC. Values are not guaranteed to be
-// monotonically non-decreasing and are subject to large amounts of skew.
-class BASE_EXPORT Time : public time_internal::TimeBase<Time> {
- public:
-  // The representation of Jan 1, 1970 UTC in microseconds since the
-  // platform-dependent epoch.
-  static const int64_t kTimeTToMicrosecondsOffset;
-
-#if !defined(OS_WIN)
-  // On Mac & Linux, this value is the delta from the Windows epoch of 1601 to
-  // the Posix delta of 1970. This is used for migrating between the old
-  // 1970-based epochs to the new 1601-based ones. It should be removed from
-  // this global header and put in the platform-specific ones when we remove the
-  // migration code.
-  static const int64_t kWindowsEpochDeltaMicroseconds;
-#else
-  // To avoid overflow in QPC to Microseconds calculations, since we multiply
-  // by kMicrosecondsPerSecond, then the QPC value should not exceed
-  // (2^63 - 1) / 1E6. If it exceeds that threshold, we divide then multiply.
-  enum : int64_t{kQPCOverflowThreshold = 0x8637BD05AF7};
-#endif
-
-  // Represents an exploded time that can be formatted nicely. This is kind of
-  // like the Win32 SYSTEMTIME structure or the Unix "struct tm" with a few
-  // additions and changes to prevent errors.
-  struct BASE_EXPORT Exploded {
-    int year;          // Four digit year "2007"
-    int month;         // 1-based month (values 1 = January, etc.)
-    int day_of_week;   // 0-based day of week (0 = Sunday, etc.)
-    int day_of_month;  // 1-based day of month (1-31)
-    int hour;          // Hour within the current day (0-23)
-    int minute;        // Minute within the current hour (0-59)
-    int second;        // Second within the current minute (0-59 plus leap
-                       //   seconds which may take it up to 60).
-    int millisecond;   // Milliseconds within the current second (0-999)
-
-    // A cursory test for whether the data members are within their
-    // respective ranges. A 'true' return value does not guarantee the
-    // Exploded value can be successfully converted to a Time value.
-    bool HasValidValues() const;
-  };
-
-  // Contains the NULL time. Use Time::Now() to get the current time.
-  Time() : TimeBase(0) {
-  }
-
-  // Returns the time for epoch in Unix-like system (Jan 1, 1970).
-  static Time UnixEpoch();
-
-  // Returns the current time. Watch out, the system might adjust its clock
-  // in which case time will actually go backwards. We don't guarantee that
-  // times are increasing, or that two calls to Now() won't be the same.
-  static Time Now();
-
-  // Returns the current time. Same as Now() except that this function always
-  // uses system time so that there are no discrepancies between the returned
-  // time and system time even on virtual environments including our test bot.
-  // For timing sensitive unittests, this function should be used.
-  static Time NowFromSystemTime();
-
-  // Converts to/from time_t in UTC and a Time class.
-  // TODO(brettw) this should be removed once everybody starts using the |Time|
-  // class.
-  static Time FromTimeT(time_t tt);
-  time_t ToTimeT() const;
-
-  // Converts time to/from a double which is the number of seconds since epoch
-  // (Jan 1, 1970).  Webkit uses this format to represent time.
-  // Because WebKit initializes double time value to 0 to indicate "not
-  // initialized", we map it to empty Time object that also means "not
-  // initialized".
-  static Time FromDoubleT(double dt);
-  double ToDoubleT() const;
-
-#if defined(OS_POSIX)
-  // Converts the timespec structure to time. MacOS X 10.8.3 (and tentatively,
-  // earlier versions) will have the |ts|'s tv_nsec component zeroed out,
-  // having a 1 second resolution, which agrees with
-  // https://developer.apple.com/legacy/library/#technotes/tn/tn1150.html#HFSPlusDates.
-  static Time FromTimeSpec(const timespec& ts);
-#endif
-
-  // Converts to/from the Javascript convention for times, a number of
-  // milliseconds since the epoch:
-  // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date/getTime.
-  static Time FromJsTime(double ms_since_epoch);
-  double ToJsTime() const;
-
-  // Converts to Java convention for times, a number of
-  // milliseconds since the epoch.
-  int64_t ToJavaTime() const;
-
-#if defined(OS_POSIX)
-  static Time FromTimeVal(struct timeval t);
-  struct timeval ToTimeVal() const;
-#endif
-
-#if defined(OS_MACOSX)
-  static Time FromCFAbsoluteTime(CFAbsoluteTime t);
-  CFAbsoluteTime ToCFAbsoluteTime() const;
-#endif
-
-#if defined(OS_WIN)
-  static Time FromFileTime(FILETIME ft);
-  FILETIME ToFileTime() const;
-
-  // The minimum time of a low resolution timer.  This is basically a windows
-  // constant of ~15.6ms.  While it does vary on some older OS versions, we'll
-  // treat it as static across all windows versions.
-  static const int kMinLowResolutionThresholdMs = 16;
-
-  // Enable or disable Windows high resolution timer.
-  static void EnableHighResolutionTimer(bool enable);
-
-  // Activates or deactivates the high resolution timer based on the |activate|
-  // flag.  If the HighResolutionTimer is not Enabled (see
-  // EnableHighResolutionTimer), this function will return false.  Otherwise
-  // returns true.  Each successful activate call must be paired with a
-  // subsequent deactivate call.
-  // All callers to activate the high resolution timer must eventually call
-  // this function to deactivate the high resolution timer.
-  static bool ActivateHighResolutionTimer(bool activate);
-
-  // Returns true if the high resolution timer is both enabled and activated.
-  // This is provided for testing only, and is not tracked in a thread-safe
-  // way.
-  static bool IsHighResolutionTimerInUse();
-#endif
-
-  // Converts an exploded structure representing either the local time or UTC
-  // into a Time class.
-  // TODO(maksims): Get rid of these in favor of the methods below when
-  // all the callers stop using these ones.
-  static Time FromUTCExploded(const Exploded& exploded) {
-    base::Time time;
-    ignore_result(FromUTCExploded(exploded, &time));
-    return time;
-  }
-  static Time FromLocalExploded(const Exploded& exploded) {
-    base::Time time;
-    ignore_result(FromLocalExploded(exploded, &time));
-    return time;
-  }
-
-  // Converts an exploded structure representing either the local time or UTC
-  // into a Time class. Returns false on a failure when, for example, a day of
-  // month is set to 31 on a 28-30 day month.
-  static bool FromUTCExploded(const Exploded& exploded,
-                              Time* time) WARN_UNUSED_RESULT {
-    return FromExploded(false, exploded, time);
-  }
-  static bool FromLocalExploded(const Exploded& exploded,
-                                Time* time) WARN_UNUSED_RESULT {
-    return FromExploded(true, exploded, time);
-  }
-
-  // Converts a string representation of time to a Time object.
-  // An example of a time string which is converted is as below:-
-  // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
-  // in the input string, FromString assumes local time and FromUTCString
-  // assumes UTC. A timezone that cannot be parsed (e.g. "UTC" which is not
-  // specified in RFC822) is treated as if the timezone is not specified.
-  // TODO(iyengar) Move the FromString/FromTimeT/ToTimeT/FromFileTime to
-  // a new time converter class.
-  static bool FromString(const char* time_string, Time* parsed_time) {
-    return FromStringInternal(time_string, true, parsed_time);
-  }
-  static bool FromUTCString(const char* time_string, Time* parsed_time) {
-    return FromStringInternal(time_string, false, parsed_time);
-  }
-
-  // Fills the given exploded structure with either the local time or UTC from
-  // this time structure (containing UTC).
-  void UTCExplode(Exploded* exploded) const {
-    return Explode(false, exploded);
-  }
-  void LocalExplode(Exploded* exploded) const {
-    return Explode(true, exploded);
-  }
-
-  // Rounds this time down to the nearest day in local time. It will represent
-  // midnight on that day.
-  Time LocalMidnight() const;
-
- private:
-  friend class time_internal::TimeBase<Time>;
-
-  explicit Time(int64_t us) : TimeBase(us) {}
-
-  // Explodes the given time to either local time |is_local = true| or UTC
-  // |is_local = false|.
-  void Explode(bool is_local, Exploded* exploded) const;
-
-  // Unexplodes a given time assuming the source is either local time
-  // |is_local = true| or UTC |is_local = false|. Function returns false on
-  // failure and sets |time| to Time(0). Otherwise returns true and sets |time|
-  // to non-exploded time.
-  static bool FromExploded(bool is_local,
-                           const Exploded& exploded,
-                           Time* time) WARN_UNUSED_RESULT;
-
-  // Converts a string representation of time to a Time object.
-  // An example of a time string which is converted is as below:-
-  // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
-  // in the input string, local time |is_local = true| or
-  // UTC |is_local = false| is assumed. A timezone that cannot be parsed
-  // (e.g. "UTC" which is not specified in RFC822) is treated as if the
-  // timezone is not specified.
-  static bool FromStringInternal(const char* time_string,
-                                 bool is_local,
-                                 Time* parsed_time);
-
-  // Comparison does not consider |day_of_week| when doing the operation.
-  static bool ExplodedMostlyEquals(const Exploded& lhs, const Exploded& rhs);
-};
-
-// static
-constexpr TimeDelta TimeDelta::FromDays(int days) {
-  return days == std::numeric_limits<int>::max()
-             ? Max()
-             : TimeDelta(days * Time::kMicrosecondsPerDay);
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromHours(int hours) {
-  return hours == std::numeric_limits<int>::max()
-             ? Max()
-             : TimeDelta(hours * Time::kMicrosecondsPerHour);
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromMinutes(int minutes) {
-  return minutes == std::numeric_limits<int>::max()
-             ? Max()
-             : TimeDelta(minutes * Time::kMicrosecondsPerMinute);
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromSeconds(int64_t secs) {
-  return FromProduct(secs, Time::kMicrosecondsPerSecond);
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromMilliseconds(int64_t ms) {
-  return FromProduct(ms, Time::kMicrosecondsPerMillisecond);
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromSecondsD(double secs) {
-  return FromDouble(secs * Time::kMicrosecondsPerSecond);
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromMillisecondsD(double ms) {
-  return FromDouble(ms * Time::kMicrosecondsPerMillisecond);
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromMicroseconds(int64_t us) {
-  return TimeDelta(us);
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromDouble(double value) {
-  // TODO(crbug.com/612601): Use saturated_cast<int64_t>(value) once we sort out
-  // the Min() behavior.
-  return value > std::numeric_limits<int64_t>::max()
-             ? Max()
-             : value < -std::numeric_limits<int64_t>::max()
-                   ? -Max()
-                   : TimeDelta(static_cast<int64_t>(value));
-}
-
-// static
-constexpr TimeDelta TimeDelta::FromProduct(int64_t value,
-                                           int64_t positive_value) {
-  return (
-#if !defined(_PREFAST_) || !defined(OS_WIN)
-          // Avoid internal compiler errors in /analyze builds with VS 2015
-          // update 3.
-          // https://connect.microsoft.com/VisualStudio/feedback/details/2870865
-          DCHECK(positive_value > 0),
-#endif
-          value > std::numeric_limits<int64_t>::max() / positive_value
-              ? Max()
-              : value < -std::numeric_limits<int64_t>::max() / positive_value
-                    ? -Max()
-                    : TimeDelta(value * positive_value));
-}
-
-// For logging use only.
-BASE_EXPORT std::ostream& operator<<(std::ostream& os, Time time);
-
-// TimeTicks ------------------------------------------------------------------
-
-// Represents monotonically non-decreasing clock time.
-class BASE_EXPORT TimeTicks : public time_internal::TimeBase<TimeTicks> {
- public:
-  // The underlying clock used to generate new TimeTicks.
-  enum class Clock {
-    LINUX_CLOCK_MONOTONIC,
-    IOS_CF_ABSOLUTE_TIME_MINUS_KERN_BOOTTIME,
-    MAC_MACH_ABSOLUTE_TIME,
-    WIN_QPC,
-    WIN_ROLLOVER_PROTECTED_TIME_GET_TIME
-  };
-
-  TimeTicks() : TimeBase(0) {
-  }
-
-  // Platform-dependent tick count representing "right now." When
-  // IsHighResolution() returns false, the resolution of the clock could be
-  // as coarse as ~15.6ms. Otherwise, the resolution should be no worse than one
-  // microsecond.
-  static TimeTicks Now();
-
-  // Returns true if the high resolution clock is working on this system and
-  // Now() will return high resolution values. Note that, on systems where the
-  // high resolution clock works but is deemed inefficient, the low resolution
-  // clock will be used instead.
-  static bool IsHighResolution();
-
-  // Returns true if TimeTicks is consistent across processes, meaning that
-  // timestamps taken on different processes can be safely compared with one
-  // another. (Note that, even on platforms where this returns true, time values
-  // from different threads that are within one tick of each other must be
-  // considered to have an ambiguous ordering.)
-  static bool IsConsistentAcrossProcesses();
-
-#if defined(OS_WIN)
-  // Translates an absolute QPC timestamp into a TimeTicks value. The returned
-  // value has the same origin as Now(). Do NOT attempt to use this if
-  // IsHighResolution() returns false.
-  static TimeTicks FromQPCValue(LONGLONG qpc_value);
-#endif
-
-  // Get an estimate of the TimeTick value at the time of the UnixEpoch. Because
-  // Time and TimeTicks respond differently to user-set time and NTP
-  // adjustments, this number is only an estimate. Nevertheless, this can be
-  // useful when you need to relate the value of TimeTicks to a real time and
-  // date. Note: Upon first invocation, this function takes a snapshot of the
-  // realtime clock to establish a reference point.  This function will return
-  // the same value for the duration of the application, but will be different
-  // in future application runs.
-  static TimeTicks UnixEpoch();
-
-  // Returns |this| snapped to the next tick, given a |tick_phase| and
-  // repeating |tick_interval| in both directions. |this| may be before,
-  // after, or equal to the |tick_phase|.
-  TimeTicks SnappedToNextTick(TimeTicks tick_phase,
-                              TimeDelta tick_interval) const;
-
-  // Returns an enum indicating the underlying clock being used to generate
-  // TimeTicks timestamps. This function should only be used for debugging and
-  // logging purposes.
-  static Clock GetClock();
-
-#if defined(OS_WIN)
- protected:
-  typedef DWORD (*TickFunctionType)(void);
-  static TickFunctionType SetMockTickFunction(TickFunctionType ticker);
-#endif
-
- private:
-  friend class time_internal::TimeBase<TimeTicks>;
-
-  // Please use Now() to create a new object. This is for internal use
-  // and testing.
-  explicit TimeTicks(int64_t us) : TimeBase(us) {}
-};
-
-// For logging use only.
-BASE_EXPORT std::ostream& operator<<(std::ostream& os, TimeTicks time_ticks);
-
-// ThreadTicks ----------------------------------------------------------------
-
-// Represents a clock, specific to a particular thread, than runs only while the
-// thread is running.
-class BASE_EXPORT ThreadTicks : public time_internal::TimeBase<ThreadTicks> {
- public:
-  ThreadTicks() : TimeBase(0) {
-  }
-
-  // Returns true if ThreadTicks::Now() is supported on this system.
-  static bool IsSupported() {
-#if (defined(_POSIX_THREAD_CPUTIME) && (_POSIX_THREAD_CPUTIME >= 0)) || \
-    (defined(OS_MACOSX) && !defined(OS_IOS)) || defined(OS_ANDROID)
-    return true;
-#elif defined(OS_WIN)
-    return IsSupportedWin();
-#else
-    return false;
-#endif
-  }
-
-  // Waits until the initialization is completed. Needs to be guarded with a
-  // call to IsSupported().
-  static void WaitUntilInitialized() {
-#if defined(OS_WIN)
-    WaitUntilInitializedWin();
-#endif
-  }
-
-  // Returns thread-specific CPU-time on systems that support this feature.
-  // Needs to be guarded with a call to IsSupported(). Use this timer
-  // to (approximately) measure how much time the calling thread spent doing
-  // actual work vs. being de-scheduled. May return bogus results if the thread
-  // migrates to another CPU between two calls. Returns an empty ThreadTicks
-  // object until the initialization is completed. If a clock reading is
-  // absolutely needed, call WaitUntilInitialized() before this method.
-  static ThreadTicks Now();
-
-#if defined(OS_WIN)
-  // Similar to Now() above except this returns thread-specific CPU time for an
-  // arbitrary thread. All comments for Now() method above apply apply to this
-  // method as well.
-  static ThreadTicks GetForThread(const PlatformThreadHandle& thread_handle);
-#endif
-
- private:
-  friend class time_internal::TimeBase<ThreadTicks>;
-
-  // Please use Now() or GetForThread() to create a new object. This is for
-  // internal use and testing.
-  explicit ThreadTicks(int64_t us) : TimeBase(us) {}
-
-#if defined(OS_WIN)
-  FRIEND_TEST_ALL_PREFIXES(TimeTicks, TSCTicksPerSecond);
-
-  // Returns the frequency of the TSC in ticks per second, or 0 if it hasn't
-  // been measured yet. Needs to be guarded with a call to IsSupported().
-  // This method is declared here rather than in the anonymous namespace to
-  // allow testing.
-  static double TSCTicksPerSecond();
-
-  static bool IsSupportedWin();
-  static void WaitUntilInitializedWin();
-#endif
-};
-
-// For logging use only.
-BASE_EXPORT std::ostream& operator<<(std::ostream& os, ThreadTicks time_ticks);
-
-}  // namespace base
-
-#endif  // BASE_TIME_TIME_H_
+// 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.
+
+// Time represents an absolute point in coordinated universal time (UTC),
+// internally represented as microseconds (s/1,000,000) since the Windows epoch
+// (1601-01-01 00:00:00 UTC). System-dependent clock interface routines are
+// defined in time_PLATFORM.cc. Note that values for Time may skew and jump
+// around as the operating system makes adjustments to synchronize (e.g., with
+// NTP servers). Thus, client code that uses the Time class must account for
+// this.
+//
+// TimeDelta represents a duration of time, internally represented in
+// microseconds.
+//
+// TimeTicks and ThreadTicks represent an abstract time that is most of the time
+// incrementing, for use in measuring time durations. Internally, they are
+// represented in microseconds. They can not be converted to a human-readable
+// time, but are guaranteed not to decrease (unlike the Time class). Note that
+// TimeTicks may "stand still" (e.g., if the computer is suspended), and
+// ThreadTicks will "stand still" whenever the thread has been de-scheduled by
+// the operating system.
+//
+// All time classes are copyable, assignable, and occupy 64-bits per
+// instance. Thus, they can be efficiently passed by-value (as opposed to
+// by-reference).
+//
+// Definitions of operator<< are provided to make these types work with
+// DCHECK_EQ() and other log macros. For human-readable formatting, see
+// "base/i18n/time_formatting.h".
+//
+// So many choices!  Which time class should you use?  Examples:
+//
+//   Time:        Interpreting the wall-clock time provided by a remote
+//                system. Detecting whether cached resources have
+//                expired. Providing the user with a display of the current date
+//                and time. Determining the amount of time between events across
+//                re-boots of the machine.
+//
+//   TimeTicks:   Tracking the amount of time a task runs. Executing delayed
+//                tasks at the right time. Computing presentation timestamps.
+//                Synchronizing audio and video using TimeTicks as a common
+//                reference clock (lip-sync). Measuring network round-trip
+//                latency.
+//
+//   ThreadTicks: Benchmarking how long the current thread has been doing actual
+//                work.
+
+#ifndef BASE_TIME_TIME_H_
+#define BASE_TIME_TIME_H_
+
+#include <stdint.h>
+#include <time.h>
+
+#include <iosfwd>
+#include <limits>
+
+#include "base/base_export.h"
+#include "base/compiler_specific.h"
+#include "base/numerics/safe_math.h"
+#include "build/build_config.h"
+
+#if defined(OS_MACOSX)
+#include <CoreFoundation/CoreFoundation.h>
+// Avoid Mac system header macro leak.
+#undef TYPE_BOOL
+#endif
+
+#if defined(OS_POSIX)
+#include <unistd.h>
+#include <sys/time.h>
+#endif
+
+#if defined(OS_WIN)
+// For FILETIME in FromFileTime, until it moves to a new converter class.
+// See TODO(iyengar) below.
+#include <windows.h>
+#include "base/gtest_prod_util.h"
+#endif
+
+namespace base {
+
+class PlatformThreadHandle;
+class TimeDelta;
+
+// The functions in the time_internal namespace are meant to be used only by the
+// time classes and functions.  Please use the math operators defined in the
+// time classes instead.
+namespace time_internal {
+
+// Add or subtract |value| from a TimeDelta. The int64_t argument and return
+// value are in terms of a microsecond timebase.
+BASE_EXPORT int64_t SaturatedAdd(TimeDelta delta, int64_t value);
+BASE_EXPORT int64_t SaturatedSub(TimeDelta delta, int64_t value);
+
+// Clamp |value| on overflow and underflow conditions. The int64_t argument and
+// return value are in terms of a microsecond timebase.
+BASE_EXPORT int64_t FromCheckedNumeric(const CheckedNumeric<int64_t> value);
+
+}  // namespace time_internal
+
+// TimeDelta ------------------------------------------------------------------
+
+class BASE_EXPORT TimeDelta {
+ public:
+  TimeDelta() : delta_(0) {
+  }
+
+  // Converts units of time to TimeDeltas.
+  static constexpr TimeDelta FromDays(int days);
+  static constexpr TimeDelta FromHours(int hours);
+  static constexpr TimeDelta FromMinutes(int minutes);
+  static constexpr TimeDelta FromSeconds(int64_t secs);
+  static constexpr TimeDelta FromMilliseconds(int64_t ms);
+  static constexpr TimeDelta FromSecondsD(double secs);
+  static constexpr TimeDelta FromMillisecondsD(double ms);
+  static constexpr TimeDelta FromMicroseconds(int64_t us);
+#if defined(OS_WIN)
+  static TimeDelta FromQPCValue(LONGLONG qpc_value);
+#endif
+
+  // Converts an integer value representing TimeDelta to a class. This is used
+  // when deserializing a |TimeDelta| structure, using a value known to be
+  // compatible. It is not provided as a constructor because the integer type
+  // may be unclear from the perspective of a caller.
+  static TimeDelta FromInternalValue(int64_t delta) { return TimeDelta(delta); }
+
+  // Returns the maximum time delta, which should be greater than any reasonable
+  // time delta we might compare it to. Adding or subtracting the maximum time
+  // delta to a time or another time delta has an undefined result.
+  static TimeDelta Max();
+
+  // Returns the internal numeric value of the TimeDelta object. Please don't
+  // use this and do arithmetic on it, as it is more error prone than using the
+  // provided operators.
+  // For serializing, use FromInternalValue to reconstitute.
+  int64_t ToInternalValue() const { return delta_; }
+
+  // Returns the magnitude (absolute value) of this TimeDelta.
+  TimeDelta magnitude() const {
+    // Some toolchains provide an incomplete C++11 implementation and lack an
+    // int64_t overload for std::abs().  The following is a simple branchless
+    // implementation:
+    const int64_t mask = delta_ >> (sizeof(delta_) * 8 - 1);
+    return TimeDelta((delta_ + mask) ^ mask);
+  }
+
+  // Returns true if the time delta is zero.
+  bool is_zero() const {
+    return delta_ == 0;
+  }
+
+  // Returns true if the time delta is the maximum time delta.
+  bool is_max() const { return delta_ == std::numeric_limits<int64_t>::max(); }
+
+#if defined(OS_POSIX)
+  struct timespec ToTimeSpec() const;
+#endif
+
+  // Returns the time delta in some unit. The F versions return a floating
+  // point value, the "regular" versions return a rounded-down value.
+  //
+  // InMillisecondsRoundedUp() instead returns an integer that is rounded up
+  // to the next full millisecond.
+  int InDays() const;
+  int InHours() const;
+  int InMinutes() const;
+  double InSecondsF() const;
+  int64_t InSeconds() const;
+  double InMillisecondsF() const;
+  int64_t InMilliseconds() const;
+  int64_t InMillisecondsRoundedUp() const;
+  int64_t InMicroseconds() const;
+
+  TimeDelta& operator=(TimeDelta other) {
+    delta_ = other.delta_;
+    return *this;
+  }
+
+  // Computations with other deltas.
+  TimeDelta operator+(TimeDelta other) const {
+    return TimeDelta(time_internal::SaturatedAdd(*this, other.delta_));
+  }
+  TimeDelta operator-(TimeDelta other) const {
+    return TimeDelta(time_internal::SaturatedSub(*this, other.delta_));
+  }
+
+  TimeDelta& operator+=(TimeDelta other) {
+    return *this = (*this + other);
+  }
+  TimeDelta& operator-=(TimeDelta other) {
+    return *this = (*this - other);
+  }
+  TimeDelta operator-() const {
+    return TimeDelta(-delta_);
+  }
+
+  // Computations with numeric types.
+  template<typename T>
+  TimeDelta operator*(T a) const {
+    CheckedNumeric<int64_t> rv(delta_);
+    rv *= a;
+    return TimeDelta(time_internal::FromCheckedNumeric(rv));
+  }
+  template<typename T>
+  TimeDelta operator/(T a) const {
+    CheckedNumeric<int64_t> rv(delta_);
+    rv /= a;
+    return TimeDelta(time_internal::FromCheckedNumeric(rv));
+  }
+  template<typename T>
+  TimeDelta& operator*=(T a) {
+    return *this = (*this * a);
+  }
+  template<typename T>
+  TimeDelta& operator/=(T a) {
+    return *this = (*this / a);
+  }
+
+  int64_t operator/(TimeDelta a) const { return delta_ / a.delta_; }
+  TimeDelta operator%(TimeDelta a) const {
+    return TimeDelta(delta_ % a.delta_);
+  }
+
+  // Comparison operators.
+  constexpr bool operator==(TimeDelta other) const {
+    return delta_ == other.delta_;
+  }
+  constexpr bool operator!=(TimeDelta other) const {
+    return delta_ != other.delta_;
+  }
+  constexpr bool operator<(TimeDelta other) const {
+    return delta_ < other.delta_;
+  }
+  constexpr bool operator<=(TimeDelta other) const {
+    return delta_ <= other.delta_;
+  }
+  constexpr bool operator>(TimeDelta other) const {
+    return delta_ > other.delta_;
+  }
+  constexpr bool operator>=(TimeDelta other) const {
+    return delta_ >= other.delta_;
+  }
+
+#if defined(OS_WIN)
+  // This works around crbug.com/635974
+  constexpr TimeDelta(const TimeDelta& other) : delta_(other.delta_) {}
+#endif
+
+ private:
+  friend int64_t time_internal::SaturatedAdd(TimeDelta delta, int64_t value);
+  friend int64_t time_internal::SaturatedSub(TimeDelta delta, int64_t value);
+
+  // Constructs a delta given the duration in microseconds. This is private
+  // to avoid confusion by callers with an integer constructor. Use
+  // FromSeconds, FromMilliseconds, etc. instead.
+  constexpr explicit TimeDelta(int64_t delta_us) : delta_(delta_us) {}
+
+  // Private method to build a delta from a double.
+  static constexpr TimeDelta FromDouble(double value);
+
+  // Private method to build a delta from the product of a user-provided value
+  // and a known-positive value.
+  static constexpr TimeDelta FromProduct(int64_t value, int64_t positive_value);
+
+  // Delta in microseconds.
+  int64_t delta_;
+};
+
+template<typename T>
+inline TimeDelta operator*(T a, TimeDelta td) {
+  return td * a;
+}
+
+// For logging use only.
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, TimeDelta time_delta);
+
+// Do not reference the time_internal::TimeBase template class directly.  Please
+// use one of the time subclasses instead, and only reference the public
+// TimeBase members via those classes.
+namespace time_internal {
+
+// TimeBase--------------------------------------------------------------------
+
+// Provides value storage and comparison/math operations common to all time
+// classes. Each subclass provides for strong type-checking to ensure
+// semantically meaningful comparison/math of time values from the same clock
+// source or timeline.
+template<class TimeClass>
+class TimeBase {
+ public:
+  static const int64_t kHoursPerDay = 24;
+  static const int64_t kMillisecondsPerSecond = 1000;
+  static const int64_t kMillisecondsPerDay =
+      kMillisecondsPerSecond * 60 * 60 * kHoursPerDay;
+  static const int64_t kMicrosecondsPerMillisecond = 1000;
+  static const int64_t kMicrosecondsPerSecond =
+      kMicrosecondsPerMillisecond * kMillisecondsPerSecond;
+  static const int64_t kMicrosecondsPerMinute = kMicrosecondsPerSecond * 60;
+  static const int64_t kMicrosecondsPerHour = kMicrosecondsPerMinute * 60;
+  static const int64_t kMicrosecondsPerDay =
+      kMicrosecondsPerHour * kHoursPerDay;
+  static const int64_t kMicrosecondsPerWeek = kMicrosecondsPerDay * 7;
+  static const int64_t kNanosecondsPerMicrosecond = 1000;
+  static const int64_t kNanosecondsPerSecond =
+      kNanosecondsPerMicrosecond * kMicrosecondsPerSecond;
+
+  // Returns true if this object has not been initialized.
+  //
+  // Warning: Be careful when writing code that performs math on time values,
+  // since it's possible to produce a valid "zero" result that should not be
+  // interpreted as a "null" value.
+  bool is_null() const {
+    return us_ == 0;
+  }
+
+  // Returns true if this object represents the maximum time.
+  bool is_max() const { return us_ == std::numeric_limits<int64_t>::max(); }
+
+  // Returns the maximum time, which should be greater than any reasonable time
+  // with which we might compare it.
+  static TimeClass Max() {
+    return TimeClass(std::numeric_limits<int64_t>::max());
+  }
+
+  // For serializing only. Use FromInternalValue() to reconstitute. Please don't
+  // use this and do arithmetic on it, as it is more error prone than using the
+  // provided operators.
+  int64_t ToInternalValue() const { return us_; }
+
+  TimeClass& operator=(TimeClass other) {
+    us_ = other.us_;
+    return *(static_cast<TimeClass*>(this));
+  }
+
+  // Compute the difference between two times.
+  TimeDelta operator-(TimeClass other) const {
+    return TimeDelta::FromMicroseconds(us_ - other.us_);
+  }
+
+  // Return a new time modified by some delta.
+  TimeClass operator+(TimeDelta delta) const {
+    return TimeClass(time_internal::SaturatedAdd(delta, us_));
+  }
+  TimeClass operator-(TimeDelta delta) const {
+    return TimeClass(-time_internal::SaturatedSub(delta, us_));
+  }
+
+  // Modify by some time delta.
+  TimeClass& operator+=(TimeDelta delta) {
+    return static_cast<TimeClass&>(*this = (*this + delta));
+  }
+  TimeClass& operator-=(TimeDelta delta) {
+    return static_cast<TimeClass&>(*this = (*this - delta));
+  }
+
+  // Comparison operators
+  bool operator==(TimeClass other) const {
+    return us_ == other.us_;
+  }
+  bool operator!=(TimeClass other) const {
+    return us_ != other.us_;
+  }
+  bool operator<(TimeClass other) const {
+    return us_ < other.us_;
+  }
+  bool operator<=(TimeClass other) const {
+    return us_ <= other.us_;
+  }
+  bool operator>(TimeClass other) const {
+    return us_ > other.us_;
+  }
+  bool operator>=(TimeClass other) const {
+    return us_ >= other.us_;
+  }
+
+  // Converts an integer value representing TimeClass to a class. This is used
+  // when deserializing a |TimeClass| structure, using a value known to be
+  // compatible. It is not provided as a constructor because the integer type
+  // may be unclear from the perspective of a caller.
+  static TimeClass FromInternalValue(int64_t us) { return TimeClass(us); }
+
+ protected:
+  explicit TimeBase(int64_t us) : us_(us) {}
+
+  // Time value in a microsecond timebase.
+  int64_t us_;
+};
+
+}  // namespace time_internal
+
+template<class TimeClass>
+inline TimeClass operator+(TimeDelta delta, TimeClass t) {
+  return t + delta;
+}
+
+// Time -----------------------------------------------------------------------
+
+// Represents a wall clock time in UTC. Values are not guaranteed to be
+// monotonically non-decreasing and are subject to large amounts of skew.
+class BASE_EXPORT Time : public time_internal::TimeBase<Time> {
+ public:
+  // The representation of Jan 1, 1970 UTC in microseconds since the
+  // platform-dependent epoch.
+  static const int64_t kTimeTToMicrosecondsOffset;
+
+#if !defined(OS_WIN)
+  // On Mac & Linux, this value is the delta from the Windows epoch of 1601 to
+  // the Posix delta of 1970. This is used for migrating between the old
+  // 1970-based epochs to the new 1601-based ones. It should be removed from
+  // this global header and put in the platform-specific ones when we remove the
+  // migration code.
+  static const int64_t kWindowsEpochDeltaMicroseconds;
+#else
+  // To avoid overflow in QPC to Microseconds calculations, since we multiply
+  // by kMicrosecondsPerSecond, then the QPC value should not exceed
+  // (2^63 - 1) / 1E6. If it exceeds that threshold, we divide then multiply.
+  enum : int64_t{kQPCOverflowThreshold = 0x8637BD05AF7};
+#endif
+
+  // Represents an exploded time that can be formatted nicely. This is kind of
+  // like the Win32 SYSTEMTIME structure or the Unix "struct tm" with a few
+  // additions and changes to prevent errors.
+  struct BASE_EXPORT Exploded {
+    int year;          // Four digit year "2007"
+    int month;         // 1-based month (values 1 = January, etc.)
+    int day_of_week;   // 0-based day of week (0 = Sunday, etc.)
+    int day_of_month;  // 1-based day of month (1-31)
+    int hour;          // Hour within the current day (0-23)
+    int minute;        // Minute within the current hour (0-59)
+    int second;        // Second within the current minute (0-59 plus leap
+                       //   seconds which may take it up to 60).
+    int millisecond;   // Milliseconds within the current second (0-999)
+
+    // A cursory test for whether the data members are within their
+    // respective ranges. A 'true' return value does not guarantee the
+    // Exploded value can be successfully converted to a Time value.
+    bool HasValidValues() const;
+  };
+
+  // Contains the NULL time. Use Time::Now() to get the current time.
+  Time() : TimeBase(0) {
+  }
+
+  // Returns the time for epoch in Unix-like system (Jan 1, 1970).
+  static Time UnixEpoch();
+
+  // Returns the current time. Watch out, the system might adjust its clock
+  // in which case time will actually go backwards. We don't guarantee that
+  // times are increasing, or that two calls to Now() won't be the same.
+  static Time Now();
+
+  // Returns the current time. Same as Now() except that this function always
+  // uses system time so that there are no discrepancies between the returned
+  // time and system time even on virtual environments including our test bot.
+  // For timing sensitive unittests, this function should be used.
+  static Time NowFromSystemTime();
+
+  // Converts to/from time_t in UTC and a Time class.
+  // TODO(brettw) this should be removed once everybody starts using the |Time|
+  // class.
+  static Time FromTimeT(time_t tt);
+  time_t ToTimeT() const;
+
+  // Converts time to/from a double which is the number of seconds since epoch
+  // (Jan 1, 1970).  Webkit uses this format to represent time.
+  // Because WebKit initializes double time value to 0 to indicate "not
+  // initialized", we map it to empty Time object that also means "not
+  // initialized".
+  static Time FromDoubleT(double dt);
+  double ToDoubleT() const;
+
+#if defined(OS_POSIX)
+  // Converts the timespec structure to time. MacOS X 10.8.3 (and tentatively,
+  // earlier versions) will have the |ts|'s tv_nsec component zeroed out,
+  // having a 1 second resolution, which agrees with
+  // https://developer.apple.com/legacy/library/#technotes/tn/tn1150.html#HFSPlusDates.
+  static Time FromTimeSpec(const timespec& ts);
+#endif
+
+  // Converts to/from the Javascript convention for times, a number of
+  // milliseconds since the epoch:
+  // https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Date/getTime.
+  static Time FromJsTime(double ms_since_epoch);
+  double ToJsTime() const;
+
+  // Converts to Java convention for times, a number of
+  // milliseconds since the epoch.
+  int64_t ToJavaTime() const;
+
+#if defined(OS_POSIX)
+  static Time FromTimeVal(struct timeval t);
+  struct timeval ToTimeVal() const;
+#endif
+
+#if defined(OS_MACOSX)
+  static Time FromCFAbsoluteTime(CFAbsoluteTime t);
+  CFAbsoluteTime ToCFAbsoluteTime() const;
+#endif
+
+#if defined(OS_WIN)
+  static Time FromFileTime(FILETIME ft);
+  FILETIME ToFileTime() const;
+
+  // The minimum time of a low resolution timer.  This is basically a windows
+  // constant of ~15.6ms.  While it does vary on some older OS versions, we'll
+  // treat it as static across all windows versions.
+  static const int kMinLowResolutionThresholdMs = 16;
+
+  // Enable or disable Windows high resolution timer.
+  static void EnableHighResolutionTimer(bool enable);
+
+  // Activates or deactivates the high resolution timer based on the |activate|
+  // flag.  If the HighResolutionTimer is not Enabled (see
+  // EnableHighResolutionTimer), this function will return false.  Otherwise
+  // returns true.  Each successful activate call must be paired with a
+  // subsequent deactivate call.
+  // All callers to activate the high resolution timer must eventually call
+  // this function to deactivate the high resolution timer.
+  static bool ActivateHighResolutionTimer(bool activate);
+
+  // Returns true if the high resolution timer is both enabled and activated.
+  // This is provided for testing only, and is not tracked in a thread-safe
+  // way.
+  static bool IsHighResolutionTimerInUse();
+#endif
+
+  // Converts an exploded structure representing either the local time or UTC
+  // into a Time class.
+  // TODO(maksims): Get rid of these in favor of the methods below when
+  // all the callers stop using these ones.
+  static Time FromUTCExploded(const Exploded& exploded) {
+    base::Time time;
+    ignore_result(FromUTCExploded(exploded, &time));
+    return time;
+  }
+  static Time FromLocalExploded(const Exploded& exploded) {
+    base::Time time;
+    ignore_result(FromLocalExploded(exploded, &time));
+    return time;
+  }
+
+  // Converts an exploded structure representing either the local time or UTC
+  // into a Time class. Returns false on a failure when, for example, a day of
+  // month is set to 31 on a 28-30 day month.
+  static bool FromUTCExploded(const Exploded& exploded,
+                              Time* time) WARN_UNUSED_RESULT {
+    return FromExploded(false, exploded, time);
+  }
+  static bool FromLocalExploded(const Exploded& exploded,
+                                Time* time) WARN_UNUSED_RESULT {
+    return FromExploded(true, exploded, time);
+  }
+
+  // Converts a string representation of time to a Time object.
+  // An example of a time string which is converted is as below:-
+  // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
+  // in the input string, FromString assumes local time and FromUTCString
+  // assumes UTC. A timezone that cannot be parsed (e.g. "UTC" which is not
+  // specified in RFC822) is treated as if the timezone is not specified.
+  // TODO(iyengar) Move the FromString/FromTimeT/ToTimeT/FromFileTime to
+  // a new time converter class.
+  static bool FromString(const char* time_string, Time* parsed_time) {
+    return FromStringInternal(time_string, true, parsed_time);
+  }
+  static bool FromUTCString(const char* time_string, Time* parsed_time) {
+    return FromStringInternal(time_string, false, parsed_time);
+  }
+
+  // Fills the given exploded structure with either the local time or UTC from
+  // this time structure (containing UTC).
+  void UTCExplode(Exploded* exploded) const {
+    return Explode(false, exploded);
+  }
+  void LocalExplode(Exploded* exploded) const {
+    return Explode(true, exploded);
+  }
+
+  // Rounds this time down to the nearest day in local time. It will represent
+  // midnight on that day.
+  Time LocalMidnight() const;
+
+ private:
+  friend class time_internal::TimeBase<Time>;
+
+  explicit Time(int64_t us) : TimeBase(us) {}
+
+  // Explodes the given time to either local time |is_local = true| or UTC
+  // |is_local = false|.
+  void Explode(bool is_local, Exploded* exploded) const;
+
+  // Unexplodes a given time assuming the source is either local time
+  // |is_local = true| or UTC |is_local = false|. Function returns false on
+  // failure and sets |time| to Time(0). Otherwise returns true and sets |time|
+  // to non-exploded time.
+  static bool FromExploded(bool is_local,
+                           const Exploded& exploded,
+                           Time* time) WARN_UNUSED_RESULT;
+
+  // Converts a string representation of time to a Time object.
+  // An example of a time string which is converted is as below:-
+  // "Tue, 15 Nov 1994 12:45:26 GMT". If the timezone is not specified
+  // in the input string, local time |is_local = true| or
+  // UTC |is_local = false| is assumed. A timezone that cannot be parsed
+  // (e.g. "UTC" which is not specified in RFC822) is treated as if the
+  // timezone is not specified.
+  static bool FromStringInternal(const char* time_string,
+                                 bool is_local,
+                                 Time* parsed_time);
+
+  // Comparison does not consider |day_of_week| when doing the operation.
+  static bool ExplodedMostlyEquals(const Exploded& lhs, const Exploded& rhs);
+};
+
+// static
+constexpr TimeDelta TimeDelta::FromDays(int days) {
+  return days == std::numeric_limits<int>::max()
+             ? Max()
+             : TimeDelta(days * Time::kMicrosecondsPerDay);
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromHours(int hours) {
+  return hours == std::numeric_limits<int>::max()
+             ? Max()
+             : TimeDelta(hours * Time::kMicrosecondsPerHour);
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromMinutes(int minutes) {
+  return minutes == std::numeric_limits<int>::max()
+             ? Max()
+             : TimeDelta(minutes * Time::kMicrosecondsPerMinute);
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromSeconds(int64_t secs) {
+  return FromProduct(secs, Time::kMicrosecondsPerSecond);
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromMilliseconds(int64_t ms) {
+  return FromProduct(ms, Time::kMicrosecondsPerMillisecond);
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromSecondsD(double secs) {
+  return FromDouble(secs * Time::kMicrosecondsPerSecond);
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromMillisecondsD(double ms) {
+  return FromDouble(ms * Time::kMicrosecondsPerMillisecond);
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromMicroseconds(int64_t us) {
+  return TimeDelta(us);
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromDouble(double value) {
+  // TODO(crbug.com/612601): Use saturated_cast<int64_t>(value) once we sort out
+  // the Min() behavior.
+  return value > std::numeric_limits<int64_t>::max()
+             ? Max()
+             : value < -std::numeric_limits<int64_t>::max()
+                   ? -Max()
+                   : TimeDelta(static_cast<int64_t>(value));
+}
+
+// static
+constexpr TimeDelta TimeDelta::FromProduct(int64_t value,
+                                           int64_t positive_value) {
+  return (
+#if !defined(_PREFAST_) || !defined(OS_WIN)
+          // Avoid internal compiler errors in /analyze builds with VS 2015
+          // update 3.
+          // https://connect.microsoft.com/VisualStudio/feedback/details/2870865
+          DCHECK(positive_value > 0),
+#endif
+          value > std::numeric_limits<int64_t>::max() / positive_value
+              ? Max()
+              : value < -std::numeric_limits<int64_t>::max() / positive_value
+                    ? -Max()
+                    : TimeDelta(value * positive_value));
+}
+
+// For logging use only.
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, Time time);
+
+// TimeTicks ------------------------------------------------------------------
+
+// Represents monotonically non-decreasing clock time.
+class BASE_EXPORT TimeTicks : public time_internal::TimeBase<TimeTicks> {
+ public:
+  // The underlying clock used to generate new TimeTicks.
+  enum class Clock {
+    LINUX_CLOCK_MONOTONIC,
+    IOS_CF_ABSOLUTE_TIME_MINUS_KERN_BOOTTIME,
+    MAC_MACH_ABSOLUTE_TIME,
+    WIN_QPC,
+    WIN_ROLLOVER_PROTECTED_TIME_GET_TIME
+  };
+
+  TimeTicks() : TimeBase(0) {
+  }
+
+  // Platform-dependent tick count representing "right now." When
+  // IsHighResolution() returns false, the resolution of the clock could be
+  // as coarse as ~15.6ms. Otherwise, the resolution should be no worse than one
+  // microsecond.
+  static TimeTicks Now();
+
+  // Returns true if the high resolution clock is working on this system and
+  // Now() will return high resolution values. Note that, on systems where the
+  // high resolution clock works but is deemed inefficient, the low resolution
+  // clock will be used instead.
+  static bool IsHighResolution();
+
+  // Returns true if TimeTicks is consistent across processes, meaning that
+  // timestamps taken on different processes can be safely compared with one
+  // another. (Note that, even on platforms where this returns true, time values
+  // from different threads that are within one tick of each other must be
+  // considered to have an ambiguous ordering.)
+  static bool IsConsistentAcrossProcesses();
+
+#if defined(OS_WIN)
+  // Translates an absolute QPC timestamp into a TimeTicks value. The returned
+  // value has the same origin as Now(). Do NOT attempt to use this if
+  // IsHighResolution() returns false.
+  static TimeTicks FromQPCValue(LONGLONG qpc_value);
+#endif
+
+  // Get an estimate of the TimeTick value at the time of the UnixEpoch. Because
+  // Time and TimeTicks respond differently to user-set time and NTP
+  // adjustments, this number is only an estimate. Nevertheless, this can be
+  // useful when you need to relate the value of TimeTicks to a real time and
+  // date. Note: Upon first invocation, this function takes a snapshot of the
+  // realtime clock to establish a reference point.  This function will return
+  // the same value for the duration of the application, but will be different
+  // in future application runs.
+  static TimeTicks UnixEpoch();
+
+  // Returns |this| snapped to the next tick, given a |tick_phase| and
+  // repeating |tick_interval| in both directions. |this| may be before,
+  // after, or equal to the |tick_phase|.
+  TimeTicks SnappedToNextTick(TimeTicks tick_phase,
+                              TimeDelta tick_interval) const;
+
+  // Returns an enum indicating the underlying clock being used to generate
+  // TimeTicks timestamps. This function should only be used for debugging and
+  // logging purposes.
+  static Clock GetClock();
+
+#if defined(OS_WIN)
+ protected:
+  typedef DWORD (*TickFunctionType)(void);
+  static TickFunctionType SetMockTickFunction(TickFunctionType ticker);
+#endif
+
+ private:
+  friend class time_internal::TimeBase<TimeTicks>;
+
+  // Please use Now() to create a new object. This is for internal use
+  // and testing.
+  explicit TimeTicks(int64_t us) : TimeBase(us) {}
+};
+
+// For logging use only.
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, TimeTicks time_ticks);
+
+// ThreadTicks ----------------------------------------------------------------
+
+// Represents a clock, specific to a particular thread, than runs only while the
+// thread is running.
+class BASE_EXPORT ThreadTicks : public time_internal::TimeBase<ThreadTicks> {
+ public:
+  ThreadTicks() : TimeBase(0) {
+  }
+
+  // Returns true if ThreadTicks::Now() is supported on this system.
+  static bool IsSupported() {
+#if (defined(_POSIX_THREAD_CPUTIME) && (_POSIX_THREAD_CPUTIME >= 0)) || \
+    (defined(OS_MACOSX) && !defined(OS_IOS)) || defined(OS_ANDROID)
+    return true;
+#elif defined(OS_WIN)
+    return IsSupportedWin();
+#else
+    return false;
+#endif
+  }
+
+  // Waits until the initialization is completed. Needs to be guarded with a
+  // call to IsSupported().
+  static void WaitUntilInitialized() {
+#if defined(OS_WIN)
+    WaitUntilInitializedWin();
+#endif
+  }
+
+  // Returns thread-specific CPU-time on systems that support this feature.
+  // Needs to be guarded with a call to IsSupported(). Use this timer
+  // to (approximately) measure how much time the calling thread spent doing
+  // actual work vs. being de-scheduled. May return bogus results if the thread
+  // migrates to another CPU between two calls. Returns an empty ThreadTicks
+  // object until the initialization is completed. If a clock reading is
+  // absolutely needed, call WaitUntilInitialized() before this method.
+  static ThreadTicks Now();
+
+#if defined(OS_WIN)
+  // Similar to Now() above except this returns thread-specific CPU time for an
+  // arbitrary thread. All comments for Now() method above apply apply to this
+  // method as well.
+  static ThreadTicks GetForThread(const PlatformThreadHandle& thread_handle);
+#endif
+
+ private:
+  friend class time_internal::TimeBase<ThreadTicks>;
+
+  // Please use Now() or GetForThread() to create a new object. This is for
+  // internal use and testing.
+  explicit ThreadTicks(int64_t us) : TimeBase(us) {}
+
+#if defined(OS_WIN)
+  FRIEND_TEST_ALL_PREFIXES(TimeTicks, TSCTicksPerSecond);
+
+  // Returns the frequency of the TSC in ticks per second, or 0 if it hasn't
+  // been measured yet. Needs to be guarded with a call to IsSupported().
+  // This method is declared here rather than in the anonymous namespace to
+  // allow testing.
+  static double TSCTicksPerSecond();
+
+  static bool IsSupportedWin();
+  static void WaitUntilInitializedWin();
+#endif
+};
+
+// For logging use only.
+BASE_EXPORT std::ostream& operator<<(std::ostream& os, ThreadTicks time_ticks);
+
+}  // namespace base
+
+#endif  // BASE_TIME_TIME_H_