Move platform abstraction to base library

src/platform/elapsed-timer.h

-// Copyright 2013 the V8 project 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 V8_PLATFORM_ELAPSED_TIMER_H_
-#define V8_PLATFORM_ELAPSED_TIMER_H_
-
-#include "src/checks.h"
-#include "src/platform/time.h"
-
-namespace v8 {
-namespace internal {
-
-class ElapsedTimer V8_FINAL BASE_EMBEDDED {
- public:
-#ifdef DEBUG
-  ElapsedTimer() : started_(false) {}
-#endif
-
-  // Starts this timer. Once started a timer can be checked with
-  // |Elapsed()| or |HasExpired()|, and may be restarted using |Restart()|.
-  // This method must not be called on an already started timer.
-  void Start() {
-    ASSERT(!IsStarted());
-    start_ticks_ = Now();
-#ifdef DEBUG
-    started_ = true;
-#endif
-    ASSERT(IsStarted());
-  }
-
-  // Stops this timer. Must not be called on a timer that was not
-  // started before.
-  void Stop() {
-    ASSERT(IsStarted());
-    start_ticks_ = TimeTicks();
-#ifdef DEBUG
-    started_ = false;
-#endif
-    ASSERT(!IsStarted());
-  }
-
-  // Returns |true| if this timer was started previously.
-  bool IsStarted() const {
-    ASSERT(started_ || start_ticks_.IsNull());
-    ASSERT(!started_ || !start_ticks_.IsNull());
-    return !start_ticks_.IsNull();
-  }
-
-  // Restarts the timer and returns the time elapsed since the previous start.
-  // This method is equivalent to obtaining the elapsed time with |Elapsed()|
-  // and then starting the timer again, but does so in one single operation,
-  // avoiding the need to obtain the clock value twice. It may only be called
-  // on a previously started timer.
-  TimeDelta Restart() {
-    ASSERT(IsStarted());
-    TimeTicks ticks = Now();
-    TimeDelta elapsed = ticks - start_ticks_;
-    ASSERT(elapsed.InMicroseconds() >= 0);
-    start_ticks_ = ticks;
-    ASSERT(IsStarted());
-    return elapsed;
-  }
-
-  // Returns the time elapsed since the previous start. This method may only
-  // be called on a previously started timer.
-  TimeDelta Elapsed() const {
-    ASSERT(IsStarted());
-    TimeDelta elapsed = Now() - start_ticks_;
-    ASSERT(elapsed.InMicroseconds() >= 0);
-    return elapsed;
-  }
-
-  // Returns |true| if the specified |time_delta| has elapsed since the
-  // previous start, or |false| if not. This method may only be called on
-  // a previously started timer.
-  bool HasExpired(TimeDelta time_delta) const {
-    ASSERT(IsStarted());
-    return Elapsed() >= time_delta;
-  }
-
- private:
-  static V8_INLINE TimeTicks Now() {
-    TimeTicks now = TimeTicks::HighResolutionNow();
-    ASSERT(!now.IsNull());
-    return now;
-  }
-
-  TimeTicks start_ticks_;
-#ifdef DEBUG
-  bool started_;
-#endif
-};
-
-} }  // namespace v8::internal
-
-#endif  // V8_PLATFORM_ELAPSED_TIMER_H_