chrome://profiler infrastructure uses base time types.

base/profiler/tracked_time.h

Index: base/profiler/tracked_time.h
diff --git a/base/profiler/tracked_time.h b/base/profiler/tracked_time.h
deleted file mode 100644
index b32f41b39cb8a6185c568c0b26c8323e3546c21b..0000000000000000000000000000000000000000
--- a/base/profiler/tracked_time.h
+++ /dev/null
@@ -1,71 +0,0 @@
-// 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.
-
-#ifndef BASE_PROFILER_TRACKED_TIME_H_
-#define BASE_PROFILER_TRACKED_TIME_H_
-
-#include <stdint.h>
-
-#include "base/base_export.h"
-#include "base/time/time.h"
-
-namespace tracked_objects {
-
-//------------------------------------------------------------------------------
-
-// TimeTicks maintains a wasteful 64 bits of data (we need less than 32), and on
-// windows, a 64 bit timer is expensive to even obtain. We use a simple

[gab, 2017/06/26 22:06:53]

Oh also, what's this "64-bit timer" referring to? Is this number used outside of
base::Timer?

[stanisc, 2017/06/26 22:33:21]

This probably refers to microsecond-precision TimeTicks value obtained via
QueryPerformanceCounter as opposed to a millisecond precision 32-bit value
returned by timeGetTime which is used as a backup when QPC method isn't well
supported by a plaform. See TimeTicks::IsHighResolution().

So the comment above is misleading when it mentions 64 bit timer.
There are two concepts that sound very similar but completely unrelated:

1) High resolution TimeTicks is what I've described above.
2) There is also high resolution system timer which affects only wait operations
with a timeout like Sleep or WaitForSingleObject and which is used for delayed
tasks. The default system timer frequency is 64 Hz which provides wakeup
precision to only about 15-16 ms. Activating the high resolution system timer
frequency gives us 1 ms wakeup precision.

[tdresser, 2017/06/27 13:21:55]

Yeah, the number of bits we use to store this information is almost completely
unrelated to which timer we use on Windows...

-// millisecond counter for most of our time values, as well as millisecond units
-// of duration between those values.  This means we can only handle durations
-// up to 49 days (range), or 24 days (non-negative time durations).
-// We only define enough methods to service the needs of the tracking classes,
-// and our interfaces are modeled after what TimeTicks and TimeDelta use (so we
-// can swap them into place if we want to use the "real" classes).
-
-class BASE_EXPORT Duration {  // Similar to base::TimeDelta.
- public:
-  Duration();
-
-  Duration& operator+=(const Duration& other);
-  Duration operator+(const Duration& other) const;
-
-  bool operator==(const Duration& other) const;
-  bool operator!=(const Duration& other) const;
-  bool operator>(const Duration& other) const;
-
-  static Duration FromMilliseconds(int ms);
-
-  int32_t InMilliseconds() const;
-
- private:
-  friend class TrackedTime;
-  explicit Duration(int32_t duration);
-
-  // Internal time is stored directly in milliseconds.
-  int32_t ms_;
-};
-
-class BASE_EXPORT TrackedTime {  // Similar to base::TimeTicks.
- public:
-  TrackedTime();
-  explicit TrackedTime(const base::TimeTicks& time);
-
-  static TrackedTime Now();
-  Duration operator-(const TrackedTime& other) const;
-  TrackedTime operator+(const Duration& other) const;
-  bool is_null() const;
-
-  static TrackedTime FromMilliseconds(int32_t ms) { return TrackedTime(ms); }
-
- private:
-  friend class Duration;
-  explicit TrackedTime(int32_t ms);
-
-  // Internal duration is stored directly in milliseconds.
-  uint32_t ms_;
-};
-
-}  // namespace tracked_objects
-
-#endif  // BASE_PROFILER_TRACKED_TIME_H_