Refactor TimeBase to post tasks. Workers to use real Idle tasks.

Source/wtf/CurrentTime.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) 2008 Google Inc. 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.
@@ skipping 35 matching lines @@
 {
     return currentTime() * 1000.0;
 }
 
 // Provides a monotonically increasing time in seconds since an arbitrary point in the past.
 // On unsupported platforms, this function only guarantees the result will be non-decreasing.
 WTF_EXPORT double monotonicallyIncreasingTime();
 
 typedef double(*TimeFunction)(void);
 void setCurrentTimeFunction(TimeFunction);
-void setMonotonicallyIncreasingTimeFunction(TimeFunction);
+WTF_EXPORT void setMonotonicallyIncreasingTimeFunction(TimeFunction);
 
 
 } // namespace WTF
 
 using WTF::currentTime;
 using WTF::currentTimeMS;
 using WTF::monotonicallyIncreasingTime;
 
 #endif // CurrentTime_h