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

public/platform/Platform.h

Index: public/platform/Platform.h
diff --git a/public/platform/Platform.h b/public/platform/Platform.h
index 722ce79bf9117ddcd0e2de4772ede0ff9dbe050d..05ea69dee424951c94fbd55c6ea52d83a4d693dc 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -425,12 +425,6 @@ public:
     // WebKit clients must implement this funcion if they use cryptographic randomness.
     virtual void cryptographicallyRandomValues(unsigned char* buffer, size_t length) = 0;
 
-    // Delayed work is driven by a shared timer.
-    typedef void (*SharedTimerFunction)();
-    virtual void setSharedTimerFiredFunction(SharedTimerFunction timerFunction) { }
-    virtual void setSharedTimerFireInterval(double) { }
-    virtual void stopSharedTimer() { }
-
     // Returns an interface to the main thread. Can be null if blink was initialized on a thread without a message loop.
     BLINK_PLATFORM_EXPORT WebThread* mainThread() const;