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 e2c461e28f2337594c3abab3a3e45f3a56713dd0..b19ef04ecfec0bfa1c25d099f53caf2f631976d7 100644
--- a/public/platform/Platform.h
+++ b/public/platform/Platform.h
@@ -441,12 +441,6 @@ 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;