Revert of Change WokerThread to use a blink::WebThread.

public/platform/WebThread.h

 /*
  * Copyright (C) 2011 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 50 matching lines @@
 
     // enterRunLoop() processes tasks posted to this WebThread. This call does not return until some task calls exitRunLoop().
     // WebThread does not support nesting, meaning that once the run loop is entered for a given WebThread it is not valid to
     // call enterRunLoop() again.
     virtual void enterRunLoop() = 0;
 
     // exitRunLoop() runs tasks until there are no tasks available to run, then returns control to the caller of enterRunLoop().
     // Must be called when the WebThread is running.
     virtual void exitRunLoop() = 0;
 
-    // Delayed work is driven by a shared timer.
-    typedef void (*SharedTimerFunction)();
-    virtual void setSharedTimerFiredFunction(SharedTimerFunction) = 0;
-    virtual void setSharedTimerFireInterval(double) = 0;
-    virtual void stopSharedTimer() = 0;
-
     virtual ~WebThread() { }
 };
 
 } // namespace blink
 
 #endif