Make Time functions go through the Platform layer.

include/v8-platform.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 59 matching lines @@
   virtual void CallOnBackgroundThread(Task* task,
                                       ExpectedRuntime expected_runtime) = 0;
 
   /**
    * Schedules a task to be invoked on a foreground thread wrt a specific
    * |isolate|. Tasks posted for the same isolate should be execute in order of
    * scheduling. The definition of "foreground" is opaque to V8.
    */
   virtual void CallOnForegroundThread(Isolate* isolate, Task* task) = 0;
 
+  /**
+   * The current time, represented as microseconds (s/1,000,000) since
+   * 00:00:00 UTC, January 1, 1970.
+   *
+   * This value can go backwards, if the system adjusts its clock.
+   */
+  virtual int64_t CurrentTime();
+
+  /**
+   * The current time, represented as microseconds (s/1,000,000) since
+   * 00:00:00 UTC, January 1, 1970.
+   *
+   * 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.
+   *
+   * This value can go backwards, if the system adjusts its clock.
+   *
+   * This function is used for timing sensitive unittests.
+   */
+  virtual int64_t CurrentTimeFromSystemTime();
+
+  /**
+   * An abstract time intended for use in measuring time durations, represented
+   * as microseconds.
+   *
+   * This is guaranteed not to decrease even if the computer clock goes
+   * backwards, but it may "stand still", for example if the computer is
+   * suspended.
+   *
+   * The resolution of this clock can be as low as 15ms, and it varies
+   * depending on hardware/operating system.
+   *
+   * This method never returns 0.
+   */
+  virtual int64_t TimeTicksNow();
+
+  /**
+   * An abstract time intended for use in measuring time durations, represented
+   * as microseconds.
+   *
+   * This is guaranteed not to decrease even if the computer clock goes
+   * backwards, but it may "stand still", for example if the computer is
+   * suspended.
+   *
+   * The implementation is hardware dependent and its return values may or may
+   * not have sub-millisecond resolution. THIS CALL IS GENERALLY MUCH MORE
+   * EXPENSIVE THAN TimeTicksNow() AND SHOULD ONLY BE USED WHEN IT IS REALLY
+   * NEEDED.
+   *
+   * This method never returns 0.
+   */
+  virtual int64_t TimeTicksHighResNow();
+
+  /**
+   * True if the TimeTicksHighResNow() returns values with high resolution.
+   */
+  virtual bool TimeTicksHasHighRes();
+
  protected:
   virtual ~Platform() {}
 };
 
 }  // namespace v8
 
 #endif  // V8_V8_PLATFORM_H_