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diff --git a/base/profiler/tracked_time.h b/base/profiler/tracked_time.h
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+// Copyright (c) 2011 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 "base/base_export.h"
+#include "base/basictypes.h"
+#include "base/time.h"
+
+namespace tracked_objects {
+
+//------------------------------------------------------------------------------
+
+#define USE_FAST_TIME_CLASS_FOR_DURATION_CALCULATIONS
+
+#if defined(USE_FAST_TIME_CLASS_FOR_DURATION_CALCULATIONS)
+
+// 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
+// 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 InMilliseconds() const;
+
+ private:
+  friend class TrackedTime;
+  explicit Duration(int32 duration);
+
+  // Internal time is stored directly in milliseconds.
+  int32 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;
+
+ private:
+  friend class Duration;
+  explicit TrackedTime(int32 ms);
+
+  // Internal duration is stored directly in milliseconds.
+  uint32 ms_;
+};
+
+#else
+
+// Just use full 64 bit time calculations, and the slower TimeTicks::Now().
+// This allows us (as an alternative) to test with larger ranges of times, and
+// with a more thoroughly tested class.
+
+typedef base::TimeTicks TrackedTime;
+typedef base::TimeDelta Duration;
+
+#endif  // USE_FAST_TIME_CLASS_FOR_DURATION_CALCULATIONS
+
+}  // namespace tracked_objects
+
+#endif  // BASE_PROFILER_TRACKED_TIME_H_