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

Source/platform/scheduler/Scheduler.h

Index: Source/platform/scheduler/Scheduler.h
diff --git a/Source/platform/scheduler/Scheduler.h b/Source/platform/scheduler/Scheduler.h
index b830ef4989e1c002ece934cb9eb89b6b551dc487..83a833b52dbee5d356041fceb301e315d5cf98a3 100644
--- a/Source/platform/scheduler/Scheduler.h
+++ b/Source/platform/scheduler/Scheduler.h
@@ -48,6 +48,10 @@ public:
     // Takes ownership of |WebThread::Task|.
     void postLoadingTask(const WebTraceLocation&, WebThread::Task*);
 
+    // For Blink Timer tasks, e.g. DOMTimers,  Can only be called from the blink main thread.
+    // Takes ownership of |WebThread::Task|.
+    void postTimerTask(const WebTraceLocation&, WebThread::Task*, long long delayMs);
+
     // Returns true if there is high priority work pending on the main thread
     // and the caller should yield to let the scheduler service that work.
     // Must be called on the main thread.