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

Source/core/workers/WorkerLoaderProxy.h

 /*
  * Copyright (C) 2009 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.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 67 matching lines @@
     ~WorkerLoaderProxy() override;
 
     void postTaskToLoader(PassOwnPtr<ExecutionContextTask>) override;
     bool postTaskToWorkerGlobalScope(PassOwnPtr<ExecutionContextTask>) override;
 
     // Notification from the provider that it can no longer be
     // accessed. An implementation of WorkerLoaderProxyProvider is
     // required to call detachProvider() when finalizing.
     void detachProvider(WorkerLoaderProxyProvider*);
 
-private:
+protected:
+    // Protected for testing.
     explicit WorkerLoaderProxy(WorkerLoaderProxyProvider*);
 
+private:
     Mutex m_lock;
     WorkerLoaderProxyProvider* m_loaderProxyProvider;
 };
 
 } // namespace blink
 
 #endif // WorkerLoaderProxy_h